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Chemsitry > Atomic Structure And The Periodic Table > Flashcards

Atomic Structure And The Periodic Table Flashcards

1
Q

Describe the reactivity of group 7 elements as you go down the group.

A

Decreases

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2
Q

Which statement best describes the arrangement of electrons in the plum pudding model?

A

Electrons are randomly arranged throughout the ball of positive charge

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3
Q

Which scientist discovered the neutron?

A

James Chadwick

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4
Q

Who discovered the plum pudding model?

A

JJ Thompson

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5
Q

What physical property is used to separate a mixture of two liquids during distillation?

A

Boiling point

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6
Q

Filtration is used to…

A

Separate an insoluble substance from a solution

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7
Q

As you go down group 1, the reactivity…

A

Increases

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8
Q

What gas is produce when an alkali metal reacts with the water?

A

Hydrogen

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9
Q

What name is given to group one elements?

A

Alkali Metals

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10
Q

What are the columns called on the periodic table?

A

Groups

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11
Q

How many electrons are there in a magnesium atom?

A

12

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12
Q

What is an element?

A

A substance that contains only one type of atom.

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13
Q

Lithium has an atomic mass of 7 and an atomic number of 3. How many neutrons are there in lithium?

A

4

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14
Q

Lithium has an atomic mass of 7 and an atomic number of 3. How many electrons are there in lithium?

A

3

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15
Q

Lithium has an atomic mass of 7 and an atomic number of 3. How many protons are there in lithium?

A

3

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16
Q

When a liquid evaporates, what happens to the movement of the particles?

A

They move faster

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17
Q

Why is it important for the results of studies on the effects of radiation to be published and shared with other scientists?

A

• To allow the findings to be independently checked
• This is known as peer review

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18
Q

What is irradiation?

A

• The process of exposing a material to nuclear radiation
• The material does not become radioactive

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19
Q

What is radioactive contamination?

A

The presence of unwanted radioactive nuclei on other materials.

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20
Q

Define the half-life of a radioactive isotope.

A

• The time it takes for the number of unstable nuclei in a substance to halve
• The time it takes for the count rate from a sample to fall to half its initial level

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21
Q

Describe the nature of radioactive decay.

A

• Random
• Which nuclei decays and when e is determined only by chance
• It is impossible to predict which nuclei will decay and when

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22
Q

State any changes to mass or charge that occur due to the emission of a gamma ray.

A

Both mass and charge remain unchanged.

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23
Q

Which type of radiation is least ionising?

A

Gamma radiation.

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24
Q

Which type of radiation is most ionising?

A

Alpha radiation

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25
Q

What will stop gamma radiation from passing through a point?

A

• Several centimetres of lead
• A few metres of concrete

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26
Q

What will stop beta radiation from passing through a point?

A

• A thin sheet of aluminium
• Several metres of air

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27
Q

What is the range of an alpha particle through air?

A

A few centimetres (normally in the range of 2-10cm).

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28
Q

State four types of nuclear radiation.

A
  1. Alpha particles
  2. Beta particles
  3. Gamma rays
  4. Neutrons
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29
Q

Give an example of a detector that may be used to measure count-rate.

A

Geiger-Muller tube

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30
Q

What is count-rate??

A

The number of radioactive decays per second for a radioactive source.

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31
Q

What is the unit of radioactive activity?

A

Becquerel (Bq)

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32
Q

Define the activity of an unstable nucleus.

A

Activity is the rate of decay of a source unstable nuclei.

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33
Q

What is the name of the process in which an unstable nucleus gives out radiation to become more stable?

A

Radioactive decay.

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34
Q

Why do unstable nuclei give out radiation?

A

• Unstable nuclei undergo decay to become more stable
• As they release radiation their stability increases

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35
Q

What did James Chadwick’s experiments on the atom prove?

A

The existence of neutrons.

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36
Q

What reinforces a scientific theory?

A

When experimental results agree with the hypothesised theoretical calculations and theories.

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37
Q

State the conclusions of the Alpha-Scattering experiment.

A

• Most of the mass of the atom is concentrated at the centre in the nucleus
• The nucleus is positively charged

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38
Q

What is the name given to the currently accepted model of the atom?

A

The Bohr nucleur model

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39
Q

Which experiment led to the plum-pudding model being discarded?

A

Rutherford’s alpha-scattering experiment.

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40
Q

Prior to the discovery of the electron what was believed about the atom?

A

The atom was believed to be indivisible.

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41
Q

How did the plum-pudding model describe the atom?

A

A ball of positive charge, with negatively charged electrons distributed evenly throughout it.

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42
Q

What may lead to a scientific model being changed or replaced?

A

The discovery of new experimental evidence which doesn’t agree with the existing theory.

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43
Q

How do atoms turn into positive ions?

A

• They lose one or more of their outer electrons
• Electrons are negatively charged, so the resultant charge of the atom is positive

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44
Q

What is an isotope of an atom?

A

An atom of an element that has a different number of neutrons, but the same number of protons.

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45
Q

What is an atom’s mass number?

A

The total number of protons and neutrons in the atom.

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46
Q

What is the name given to the number of protons in an atom?

A

Atomic Number

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47
Q

What do all forms of the same element have in common?

A

They all have the same number of protons.

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48
Q

How does the ratio of electrons to protons in an atom result in the atom having no overall charge?

A

• The number of protons is equal to the number of electrons
• Protons and electrons have equal and opposite charges, so charge cancels

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49
Q

Explain how an atom’s electron arrangement changes when it emits EM radiation.

A

• Electrons move closer to the nucleus
• They move to a lower energy level

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50
Q

Give two ways that an atom’s electron arrangement can be changed.

A
  1. Absorbing electromagnetic radiation
  2. Emitting electromagnetic radiation
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51
Q

What type of charge does the nucleus of an atom have? Why?

A

• Positive charge
The nucleus contains protons and neutrons
• Protons have a positive charge
• Neutrons have no charge

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52
Q

Describe the arrangement of protons, neutrons and electrons in an atom.

A

• The protons and neutrons are found in the atom’s nucleus
• The electrons are found in discrete energy levels around the nucleus

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53
Q

Approximately what proportion of the total radius of an atom is the radius of the nucleus?

A

1/10,000

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54
Q

Where is most of the mass of an atom concentrated?

A

In the nucleus

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55
Q

What are the three subatomic constituents of an atom?

A
  1. Proton
  2. Neutron
  3. Electron
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56
Q

What is potassiums reaction with water?

A
  • quicker reaction time compared to Na
  • fizzed around the lilac flame was seen
  • hydrogen gas was given off
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57
Q

What is sodium’s reaction with water?

A
  • quicker reaction time compared to Li
  • fizzed around on the surface and rolled into ball
  • hydrogen gas was given off
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58
Q

What is lithium’s reaction with water?

A
  • took a while to react
  • fizzed around on the surface
  • hydrogen gas was given off
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59
Q

What are some of the noble gases used for?

A
  • helium is used in party balloons
  • neon is used in advertising signs
  • krypton is used in lasers designed for laser eye surgery
  • argon is used in lightbulbs to stop the filament reacting with oxygen.
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60
Q

What is different about group 0
(The Noble Gases)

A
  • the boiling points of the noble gases increase with increasing atomic mass (going down the group)
  • don’t form molecules because their full outer shell gives them a
    “stable electron arrangement”
  • very unreactive because they have full outer shells.
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61
Q

What are the differences of the development of the periodic table?

A
  • Newlands said that every eight elements with similar properties, which Mendeleev state of the elements in group have similar properties.
  • Mendeleev left gaps for the elements that he said that were not discovered yet; he was correct and left the correct gaps.
  • The reaction that Newlands got was negative by other scientists, as Newlands grouped differently related elements together, while Mendeleev got a curious reaction, then that turned into a useful tool.
  • Mendeleev swapped elements around if he thought they were in the wrong positions, while Newlands never changed any elements around.
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62
Q

What are the similarities of the development of the periodic table?

A
  • both Newlands and Mendeleev ordered elements by their increasing atomic mass
  • both scientists added all elements known at the time to their version of the table
  • both scientist produced tables in which elements with similar properties were placed at regular intervals
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63
Q

What is the relative mass of an electron?

A

Very small

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64
Q

What is the relative mass of a neutron?

A

1

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65
Q

What is the relative mass of a proton?

A

1

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66
Q

What is the relative charge of an electron?

A

-1

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67
Q

What is the Nucleur model?

A

Positively charged alpha particles were fired at gold atoms. The majority of alpha particles pass straight through this provided the atom is mostly empty space. A tiny proportion of the alpha particles deflect back at large angles. This suggested that the atom had a tiny nucleus. Because the alpha particles are positive and were repelled by the nucleus, this means the nucleus also has a positive charge.

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68
Q

Who created the plum pudding model?

A

JJ Thomson

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69
Q

What did later experiments lead to the idea of?

A

Later experiments led to the idea that the positive charge of any nucleus can be subdivided into a whole number of smaller species each particle having the same amount of positive charge. The name proton was given to these particles.

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70
Q

What are the different physical seperation methods?

A
  • filtration
  • crystallisation
  • simple distillation
  • chromatography
  • fractional distillation
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71
Q

How are mixtures separated?

A

Mixtures can be separated by physical processes, such as filtration, crystallisation, simple, distillation, fractional distillation and chromatography. These physical processes do not involve chemical reactions and no new substances are made.

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72
Q

What are the physical properties of group 1?

A
  • soft - get softer going down the group.
  • have relatively low melting points.
  • have low densities.
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73
Q

What does it mean if an element has a full outer shell?

A
  • they are unreactive
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74
Q

In group 0 what happens as you go down the group?

A

Going down the group boiling point increases because:
- atoms are larger.
- intermolecular forces between atoms increase.
- more energy is required to overcome them.

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75
Q

Which group has a full outer shell?

A

Group 0 - the noble gases

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76
Q

What is distillation?

A

Seperating mixtures of liquids of different boiling points.

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77
Q

What is crystillistion?

A

Seperating a soluble solid from a solution.

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78
Q

What is filtration?

A

Seperating an insoluble base from a liquid.

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79
Q

What did James Chadwick discover about neutrons?

A
  • discovered particles with a mass but no charge.
  • named these particles neutrons.
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80
Q

Who discovered neutrons?

A

James Chadwick

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81
Q

What did Niels Bohr discover about electron shells?

A
  • determined that electrons are held in shells, or energy shells.
  • determined that protons, with a positive charge, are in the nucleus of each atom.
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82
Q

Who discovered electron shells?

A

Neils Bohr

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83
Q

What did Ernest Rutherford conclude in the Nucleur model?

A
  • the mass of an atom is concentrated in the centre of the atom - the nucleus.
  • the nucleus is positively charged.
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84
Q

Who created the Nucleur model?

A

Ernest Rutherford

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85
Q

What is the Nucleur model?

A
  • carried out the gold foil experiment.
  • he fired positively charged alpha particles at a thin sheet of gold foil.
  • expected all particles to go straight through.
  • most did, but some scattered ir different directions.
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86
Q

What is the maximum electron configuration?

A

2,8,8

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87
Q

What does the number of electrons mean?

A

The atomic number

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88
Q

What does the number of neutrons mean?

A

[Number of neutrons = the atomic
number

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89
Q

What does the number of protons mean?

A

The atomic number

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90
Q

What does the bottom number on the periodic table elements mean?

A
  • the smaller number is the atomic (proton) number
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91
Q

What does the top number on the periodic table elements mean?

A
  • the larger number is the relative atomic mass (RAM).
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92
Q

What is the relative charge of an electron?

A

-1

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93
Q

What is the relative charge of a neutron?

A

0

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94
Q

What is the atomic mass of an electron?

A

1/1840

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95
Q

What is the atomic mass of a neutron?

A

1

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96
Q

What is the atomic mass of the proton?

A

1

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97
Q

What are the qualities of an atom?

A
  • has a central nucleus surrounded by electrons arranged in shells.
  • the nucleus comprises protons and neutrons.
  • the nucleus is less 1/10,000 the overall size of an atom.
  • the remaining space between the electron and nucleus is empty.
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98
Q

What is the relative atomic mass?

A

The number of protons and neutrons in an atom.

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99
Q

What is a proton?

A

A positively charged subatomic particle. Has a relative atomic mass of 1. In the nucleus of an atom.

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100
Q

What is the nucleus?

A

Found in the centre of an atom.
Compromises protons and neutrons (except hydrogen, which is just one proton and neutrons).

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101
Q

What is a neutron?

A

A neutrally charged subatomic particle. Has a relative atomic mass of 1. In the nucleus of the atom.

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102
Q

What is a mixture?

A

Two or more elements or compounds chemically bonded to one another.

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103
Q

What is an isotope?

A

A group of atoms with the same number of protons but different numbers of neutrons.

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104
Q

What is an ion?

A

An atom or group of atoms which has gained or lost electrons to become charged.

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105
Q

What is energy level (shells)?

A

Shells surrounding the nucleus that the electrons occupy.

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106
Q

What is an element?

A

A substance comprimising only one type of atom. Each atom has the same number of an atom.

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107
Q

What is an electron?

A

A negatively charged subatomic particle. Has a very small relative atomic mass. Orbits the nucleus of an atom.

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108
Q

What is a compound?

A

A substance with two or more elements chemical bonded to each other.

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109
Q

What is an atomic number?

A

Number of protons in an element.

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110
Q

What is an atom?

A

The smallest part of an element that can exist.

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111
Q

Why is alpha radiation the most ionising?

A

Alpha is the most ionising due to the fact it has the highest charge

112
Q

Why is alpha radiation the most ionising?

A

Alpha is the most ionising due to the fact it has the highest charge.

113
Q

What happens when atoms in
DNA become ionised?

A

Mutations and can lead to cancer.

114
Q

What is contamination?

A

Contamination is when an object is mixed with a radioactive substance.

115
Q

What is irradiation?

A

Irradiation is when a surface is exposed to radiation.

116
Q

Before measuring the current rate of a radioactive source, what must you measure?

A

Background count rate

117
Q

Why is the beta particle emitted?

A

An electron is created in the nucleus and instantly emitted.

118
Q

What happens to the alpha particle emitted?

A

Two protons and two neutrons are emitted as an alpha particle.

119
Q

In beta decay, what is the change in nucleus?

A

Neutrons in the nucleus turns into a proton.

120
Q

In alpha decay, what is the change in nucleus?

A

Nucleus loses two protons and two neutrons.

121
Q

Why did they call the centre of the atom a nucleus?

A

They called the centre the nucleus and knew it was positive because alpha particles which have a positive charge of 2+, meant that they will deflect off.

122
Q

Why did they call the centre of the atom a nucleus?

A

They called the centre the nucleus and knew it was positive because alpha particles which have a positive charge of 2+, meant that they will deflect off.

123
Q

Why did they call the centre of the atom the nucleus?

A

They called the centre the nucleus and knew it was positive because alpha particles which have a positive charge of 2+, meant that they will deflect off.

124
Q

In Rutherford’s scattering experiment, what did the deflected particles lead to?

A

Some were deflected through large angles - the plum pudding model cannot explain this. These reflections meant that the centre of an atom must consist of a positive charge.

125
Q

What is one man-made source of radiation?

A

Nucleur Power Plants

126
Q

What is one example of a natural source of background radiation?

A
  • rocks
  • food
  • cosmic rays
127
Q

What are the three types of radiation?

A

Alpha, Beta and Gamma.

128
Q

[What is the type of particle found outside the nucleus?

A

Electrons

129
Q

What is the description of gamma rays?

A

Waves with very high energies and short wavelengths.

130
Q

What is the description for beta particles?

A

Is a stream of fast moving electrons.

131
Q

What is the charge of neutrons?

A

Neutrons have no charge.

132
Q

What is the nucleus made up of?

A
  • Protons
  • Neutrons
  • No electrons
133
Q

What are protons made up of?

A

Positive charge

134
Q

What does the emission of a gamma ray cause?

A

The emission of a gamma ray does not cause the mass or the charge of the nucleus to change.

135
Q

What does beta decay cause?

A

Beta decay does not cause the mass of the nucleus to change but does causes the charge of the nucleus to increase.

136
Q

What does alpha decay cause?

A

Alpha decay causes both the mass and charge of the nucleus to decrease.

137
Q

What is a beta particle represented by?

A

0
-1. e

138
Q

What are gamma rays absorbed by?

A

Concrete

139
Q

What are beta particles absorbed by?

A

Aluminium

140
Q

What are alpha particles absorbed by?

A

Paper

141
Q

What does the type of radiation emitted affect?

A

The type of radiation emitted affects the level of hazard.

142
Q

What is the hazard of radioactive contamination?

A

The hazard from contamination is due to the decay of the contaminating atoms.

143
Q

What is radioactive contamination?

A

The unwanted presence of materials containing radioactive atoms on other materials.

144
Q

What is the half life of a radioactive isotope?

A

The half life of radioactive isotope is the time it takes from the number of nuclei of the isotope in a sample to half, all the time and takes on the count rate from a sample containing the isotope to fall to half its initial value.

145
Q

Is radioactive decay random or programmed?

A

Radioactive decay is random.

146
Q

How does the nucleus make the atomic nuclei more stable?

A

The nucleus gives out radiation as it changes to become more stable.

147
Q

What did the experimental work of James Chadwick prove?

A

Experimental work of James Chadwick proved the evidence to show the existence of neutrons within the nucleus. This was about 20 years after the nucleus became an adapted scientific idea.

148
Q

What did later investigations of positive charge and the nucleus lead to?

A

Later experiments led to the idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles, each particle having the same amount of positive charge. The name proton was given to these particles.

149
Q

How did Niels Bohr adapt the nuclear model?

A

Niels Bohr adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances.

150
Q

What did the nuclear model replace?

A

The plum pudding model.

151
Q

What are the results from the alpha particle scattering experiment lead to?

A
  • the mass of an atom was concentrated at the centre.
  • the nucleus was charged.
152
Q

Before the discovery of the electron, what were atoms thought to be?

A

Before the discovery of the electron, atoms were thought to be tiny spheres that could not be divided.

153
Q

What happens to an atom if they lose one or more outer electrons?

A

Atoms turn into positive ions if they lose one or more outer electrons.

154
Q

What is it called when atoms of the same element have different numbers of neutrons?

A

Atoms of the same element have different numbers of neutrons; these atoms are called isotopes of that element.

155
Q

Is the atomic number the number at the top or the bottom?

A

Bottom

156
Q

Is the mass number the number at the top or bottom?

A

Top

157
Q

The total number of ____ and ____ in an atom is called its mass number.

A

Protons and Neutrons

158
Q

What is the name of the number of protons in an element?

A

The number of protons in an atom of an element is called its atomic number.

159
Q

All atoms of a particular element have the same number of ____.

A

Protons

160
Q

What is the charge of an atom?

A

Atoms have no overall electrical charge.

161
Q

Why may the electron arrangement move?

A

The electron arrangements may change with the absorption of electromagnetic radiation (move further from the nucleus; a higher energy level) or by the emissions of electromagnetic radiation (move closer to the nucleus; a lower energy level).

162
Q

How are electrons arranged around the nucleus?

A

The electrons are arranged at different distances from the nucleus.

163
Q

Where is the most of the mass of an atom concentrated?

A

In the nucleus.

164
Q

Where is the most of the mass of an atom concentrated?

A

In the nucleus.

165
Q

What is the radius of the nucleus?

A

The radius of the nucleus is less than 1/10,000 of the radius of an atom.

166
Q

What is the basic structure of an atom?

A

The basic structure of an atom is it a positively charged nucleus composed of both protons and neutrons surrounded by negatively charged electrons.

167
Q

What size are atoms?

A

Atoms are very small

168
Q

What are all substances made up of?

A

All substances are made of tiny particles of matter called atoms which are the building blocks of all matter

169
Q

Where are the protons and neutrons in the atom?

A

Located at the centre of the cell, in the nucleus.

170
Q

Where do the electrons move?

A

The electrons move very fast around the nucleus in orbital paths called shells.

171
Q

What is an element?

A

An element is a substance made of atoms that all contain the same number of protons and cannot be split into anything simpler.

172
Q

Where are the elements found?

A

All the elements are found in the periodic table.

173
Q

How many elements does the most recent periodic table contain?

A

The most recent Periodic Tables commonly contain around 103 elements although some go up to 118 elements.

174
Q

What happens when elements take part in a chemical reaction?

A

Elements take part in chemical reactions in which new substances are made in processes that most often involve an energy change

175
Q

What is a compound?

A
  • A compound is a pure substance made up of two or more elements chemically combined and which cannot be separated by physical means.
176
Q

What do ionic compounds contain?

A

Ionic compounds contain metal and non-metal elements joined together as particles called ions

177
Q

What happens to the non-metal element?

A
  • The non-metal element always takes on the name ending ‘– ide’ unless oxygen is also present.
  • For example, PbS is called lead sulfide and MgCl2 is called magnesium chloride.
178
Q

What happens in a compound when oxygen is present?

A

When oxygen is present the name ending is usually ‘-ate’
For example, CuSO4 is copper sulphate, KClO3 is potassium chlorate and Na2CO3 is sodium carbonate

179
Q

What do covalent compounds contain?

A

Covalent compounds contain only non-metals

180
Q

What are non-metals named using?

A
  • They are named using prefixes (mono, di, tri, tetra, penta) to show how many of each element is present in the formula.
  • For example, CO2 is carbon dioxide, NO is nitrogen monoxide and SiCl4 is silicon tetrachloride.
181
Q

What does H2SO4 stand for?

A

Sulfuric Acid

182
Q

What does NH3 stand for?

A

Ammonia

183
Q

What does CH4 stand for?

A

Methane

184
Q

What does HCl stand for?

A

Hydrochloric acid

185
Q

What does C6H12O6 stand for?

A

Glucose

186
Q

What does C2H5OH stand for?

A

Ethanol

187
Q

What does HNO3 stand for?

A

Nitric acid

188
Q

What do word equations show?

A

These show the reactants and products of a chemical reaction using their full chemical names

189
Q

Where are the reactants found?

A

The reactants are those substances on the left-hand side of the arrow and can be thought of as the chemical ingredients of the reaction

190
Q

Where are the new substances found?

A

The products are the new substances which are on the right-hand side of the arrow

191
Q

What does a symbol equation show?

A

A symbol equation uses the formulae of the reactants and products to show what happens in a chemical reaction

192
Q

What happens to substances before and after chemical reactions?

A

New substances are made during chemical reactions.
- However, the same atoms are always present before and after reaction.
- They have just joined up in different ways.
- Atoms cannot be created or destroyed, so if they exist in the reactants then they absolutely must be in the products!

193
Q

What is the total mass of reactants equal to?

A

Because of this the total mass of reactants is always equal to the total mass of products

194
Q

What does the law of conservation of mass allow?

A

The Law of Conservation of Mass enables us to balance chemical equations, since no atoms can be lost or created

195
Q

What do half equations show?

A

Half equations are used to show what happens to the electrons in reactions where atoms, molecules or ions are gaining or losing electrons.

196
Q

Why are half equations called half equations?

A
  • They are called half equations, because they represent only half of what is happening in a reaction involving electron transfer
  • One species gains electrons
  • Another species loses electrons
197
Q

What are examples of half equations?

A

Pb2+ + 2e- → Pb

2Br- → Br2 + 2e-

198
Q

What do ionic equations indicate?

A

Ionic equations are used to indicate what happens to ions during reactions

199
Q

What do ionic equations help to do?

A

They help to simplify complicated processes where many substances are present, but only certain ions are actually reacting with each other

200
Q

What are ions that are present but do not take part in the reaction called?

A

Spectator Ions

201
Q

What do mixtures contain?

A

Mixtures can contain elements and / or compounds.

202
Q

How are substances joined in a mixture?

A
  • The parts of a mixture are not chemically bonded together and so they can be separated by physical means.
  • The choice of the method of separation depends on the nature of the substances being separated
203
Q

How is a mixture separated?

A
  • All methods rely on there being a difference in a physical property such as the boiling point or solubility, between the substances being separated
204
Q

How is filtration used?

A
  • Used to separate an undissolved solid from a mixture of the solid and a liquid / solution ( e.g., sand from a mixture of sand and water).
  • Centrifugation and decanting can also be used for this mixture.
205
Q

What are the steps to filtering something?

A
  • A piece of filter paper is placed in a filter funnel above a beaker.
  • A mixture of insoluble solid and liquid is poured into the filter funnel.
  • The filter paper will only allow small liquid particles to pass through as filtrate.
  • Solid particles are too large to pass through the filter paper so will stay behind as a residue.
206
Q

What is crystallisation? How does it work?

A
  • Used to separate a dissolved solid from a solution, when the solid is much more soluble in hot solvent than in cold (e.g., copper sulphate from a solution of copper (II) sulphate in water).
207
Q

How does crystallisation take place?

A
  • The solution is heated which allows the solvent to evaporate and leaves a saturated solution.
  • To test if the solution is saturated a clean, dry, cold glass rod is dipped into the solution.
  • If the solution is saturated, crystals will form on the glass rod.
  • The saturated solution is then allowed to cool slowly.
  • Crystals begin to grow as solids come out of solution due to decreasing solubility.
  • The crystals are collected by filtering the solution, they are washed with cold distilled water to remove impurities and are then allowed to dry.
208
Q

What is simple distillation?

A

This is used to separate a liquid and soluble solid from a solution (e.g., water from a solution of salt water) or a pure liquid from a mixture of liquids.

209
Q

How does simple distillation take place?

A
  • The solution is heated and a liquid evaporates producing a vapour which rises through the neck of the round-bottomed flask (e.g. for saltwater, this would be water boiling at 100 oC).
  • The vapour passes through the condenser, where it cools and condenses, turning into the pure liquid that is collected in a beaker.
  • After all the liquid is evaporated from the solution, only the solid solute will be left behind.
210
Q

What is fractional distillation?

A

This is used to separate two or more liquids that are miscible with one another (e.g., ethanol and water from a mixture of the two).

211
Q

What are the steps to fractional distillation? 

A
  • The solution is heated to the temperature of the substance with the lowest boiling point.
  • This substance will rise and evaporate first, and vapours will pass through a condenser, where they cool and condense, turning into a liquid that will be collected in a beaker.
  • All of the substance is evaporated and collected, leaving behind the other components(s) of the mixture.
    For water and ethanol
  • Ethanol has a boiling point of 78 ºC and water of 100 ºC.
  • The mixture is heated until it reaches 78 ºC, at which point the ethanol boils and distills out of the mixture and condenses into the beaker.
  • When the temperature starts to increase to 100 ºC heating should be stopped. Water and ethanol are now separated.
212
Q

What is paper chromatography? 

A

This technique is used to separate substances that have different solubilities in a given solvent (e.g., different coloured inks that have been mixed to make black ink).

213
Q

How is paper chromatography carried out?

A
  1. A pencil line is drawn on chromatography paper and spots of the sample are placed on it. Pencil is used for this as ink would run into the chromatogram along with the samples.
  2. The paper is then lowered into the solvent container, making sure that the pencil line sits above the level of the solvent, so the samples don’t wash into the solvent container.
  3. The solvent travels up the paper by capillary action, taking some of the coloured substances with it.
  4. Different substances have different solubilities so will travel at different rates, causing the substances to spread apart.
    - Those substances with higher solubility will travel further than the others.
  5. This will show the different components of the ink / dye
    If two or more substances are the same, they will produce identical chromatograms.
  6. If the substance is a mixture, it will separate on the paper to show all the different components as separate spots.
  7. An impure substance will show up with more than one spot, a pure substance should only show up with one spot.
214
Q

What is the equipment required for paper chromatography? 

A
  • Chromatography paper
  • Pencil
  • Different inks
  • Beaker
  • Solvent
  • Ruler
215
Q

When did John Dalton present his atomic theory?

A

1803

216
Q

What are the three key ideas John Dalton’s atomic theory was based on?

A
  • Matter is made of atoms which are tiny particles that cannot be created, destroyed, or divided.
  • Atoms of the same element are identical, and atoms of different elements are different.
  • Different atoms combine together to form new substances.
217
Q

When did Dalton “Billard Ball” Model come into existence?

A

1803

218
Q

When did Thomson “PLUM PUDDING” Model come into existence?

A

1897

219
Q

When did Rutherford model come into existence?

A

1909-1911

220
Q

When did Niels “Bohr Model” come into existence?

A

1913

221
Q

When did the Quantum mechanical model come into existence?

A

1926

222
Q

In 1897, what did physicist JJ Thompson, discover? 

A

The electron

223
Q

How did JJ Thompson discover the electron?

A
  • Using a cathode-ray tube, he conducted an experiment which identified the electron as a negatively charged subatomic particle, hence proving that atoms are divisible.
224
Q

What did JJ Thompson’s theory lead to?

A
  • Based on his investigations, Thomson proposed a model of the atom known as the plum pudding model which depicted negative electrons spread throughout soft globules of positively charged material.
225
Q

What did Ernest Rutherford base his model off of?

A

In 1909, Ernest Rutherford presented his model of the atom based on the famous gold foil experiment

226
Q

What is the gold foil experiment?

A

Rutherford shot a beam of positively charged particles at a thin sheet of gold foil and based on the plum pudding model, expected the particles to pass through the foil because the positive charge of the nucleus was thought to be evenly spread out

227
Q

What happened to some of the particles shot at the gold foil?

A

Some particles were scattered, however, and a few were deflected directly back, which led him to postulate that most of an atom’s mass is concentrated in a region of space at the centre of the atom called the nucleus

228
Q

Was Rutherford scattering idea similar to the plum pudding model?

A

The results of Rutherford’s scattering experiments did not support the idea that atoms were as described in the plum pudding model, so the model had to be changed.

229
Q

What does Rutherford’s model consist of?

A

In Rutherford’s model, the atom consists mainly of empty space with the nucleus at the centre and the electrons orbiting in paths around the nucleus.

230
Q

What was Rutherford’s scattering model known as?

A
  • This model was known as the nuclear model of the atom.
231
Q

What is the difference between the Plum Pudding Model and Rutherford Scattering experiment?

A
  • In the plum pudding model, atoms were described as being made from electrons embedded within a positive sphere, whereas in the nuclear model the nucleus is a positive structure at the centre of the atom, with negative (and much smaller) electrons ‘orbiting’ around the outside of it.
232
Q

What does the Bohr Model show?

A
  • In 1913, Niels Bohr further developed the nuclear model by proposing that electrons orbit the nucleus in fixed shells or orbitals located at set distances from the nucleus.
233
Q

In the Bohr Model, what does each orbital have?

A
  • Each orbital has a different energy associated with it, with the higher energy orbitals being located further away from the nucleus.
234
Q

What did the Bohr model solve?

A

This model solved the question of why the atom does not collapse inwards due to the attraction between the positive nucleus and negative electrons circling the nucleus.

235
Q

What did Bohr’s theory agree with?

A

Bohr’s theory and calculations agreed with experimental results

236
Q

What did further investigation of the Bohr Model lead to?

A
  • Further investigation and experimentation revealed that the nucleus could be divided into smaller particles, each one having the same mass and charge.
  • This work led to the discovery of the proton.
237
Q

What did Rutherford put forward in 1920?

A
  • In 1920, Rutherford put forward the idea of the existence of large, neutral particles within the nucleus.
  • His idea was based on the differences between the atomic mass and the atomic number of atoms.
238
Q

What did James Chadwick publish in 1932?

A

In 1932, James Chadwick published a paper based on an experiment carried out by Frédéric and Irène Joliot-Curie which provided evidence for the existence of these neutral particles which were called neutrons.

239
Q

What charge do atoms have overall?

A
  • Atoms are neutral overall.
  • Even though they contain charged subatomic particles, the charges cancel each other out in an atom.
240
Q

What are the size of atoms?

A

Atoms are extremely small with a radius of about 1 x 10^-10 metres or 0.1 nanometres

241
Q

What size is the radius of the nucleus?

A
  • The radius of the nucleus is about 10 000 times smaller than that of the atom, around 1 x 10-14 m, so it is an extremely small region of space compared to the overall size of the atom.
242
Q

What is the mass of electrons?

A
  • Electrons have a much smaller mass than protons and neutrons (1 proton has the same mass of around 1840 electrons) and move in the space outside the nucleus in orbits.
243
Q

What is the atomic number?

A

The atomic number or proton number is the number of protons in the nucleus of an atom.
- It is also the number of electrons present in an atom and determines the position of the element on the periodic table.

244
Q

Why is the proton number unique?

A

The proton number is unique to each element, so no two elements have the same number of protons

245
Q

What happens to electrons?

A

Electrons can be lost, gained, or shared during chemical processes but the proton number of an atom does not change in a chemical reaction.

246
Q

What does mass mean?

A

MASS = MASSIVE
- mass number is always the bigger of the two numbers, the other smaller one is thus the atomic / proton number.

247
Q

What is the mass number?

A

The mass number (or nucleon number) is the total number of protons and neutrons in the nucleus of an atom
The symbol for this number is A

248
Q

How do you find the number of neutrons in an atom?

A
  • The nucleon number minus the proton number gives you the number of neutrons of an atom.
  • Note that protons and neutrons can collectively be called nucleons.
249
Q

What are isotopes?

A
  • Isotopes are atoms of the same element that contain the same number of protons and electrons but a different number of neutrons.
250
Q

What do isotopes display?

A
  • Isotopes display the same chemical characteristics.
  • This is because they have the same number of electrons in their outer shells, and this is what determines their chemistry.
251
Q

What is the difference between isotopes?

A
  • The difference between isotopes is the neutrons which are neutral particles within the nucleus and add mass only.
252
Q

Can isotopes be two different elements?

A

For atoms to be isotopes of each other, they must both be from the same element, hence they must have the same atomic number. E.g., C-13 and C-14 are isotopes whereas C-13 and H-2 are not.

253
Q

What is the atomic number equal to?

A

Atomic number = Protons

254
Q

What do atoms have the same number as?

A

Since atoms are neutral, then it is also the same as the number of electrons (e).

255
Q

What is the mass number made up of?

A
  • The mass number is the number of protons plus neutrons.
256
Q

How can the number of neutrons be calculated?

A
  • The number of neutrons (n) can thus be calculated by subtracting the atomic number from the mass number.
257
Q

What is relative atomic mass used for?

A
  • Atoms are so tiny that we cannot really compare their masses in conventional units such as kilograms or grams, so a unit called the relative atomic mass (Ar) is used.
258
Q

What is the relative atomic mass equal to?

A
  • The relative atomic mass unit is equal to 1/12th the mass of a carbon-12 atom.
259
Q

How do you calculate Ar?

A

Ar = (% of isotope A x mass of isotope A) + (% of isotope B x mass of isotope B) / 100

260
Q

What is the electrons role in the atom?

A
  • Electrons orbit the nucleus in shells.
261
Q

Was each shell the same?

A
  • Each shell has a different amount of energy associated with it.
  • The further away from the nucleus, the more energy a shell has.
262
Q

What happens when the shell becomes full of electrons?

A
  • When a shell becomes full of electrons, additional electrons have to be added to the next shell.
263
Q

What is the electron shell configuration?

A
  • 2 electrons …
  • 8 electrons …
  • 8 electrons …
264
Q

What is the outermost shell called?

A
  • The outermost shell of an atom is called the valence shell and an atom is much more stable if it can manage to completely fill this shell with electrons.
265
Q

What happens if the outer shell is not filled?

A
  • In most atoms, the outermost shell is not full and therefore these atoms react with other atoms in order to achieve a full outer shell of electrons (which would make them more stable).
  • In some cases, atoms lose electrons to entirely empty this shell so that the next shell below becomes a (full) outer shell.
266
Q

What is a period?

A

The red numbers at the bottom show the number of notations which is 3, showing that a chlorine atom has 3 shells of electrons

267
Q

What is a group?

A

The last notation, in this case 7, shows that chlorine has 7 outer electrons, and therefore is in group 7

268
Q

How are the elements in the periodic table arranged?

A
  • Elements are arranged on the periodic table in order of increasing atomic number.
  • Each element has one proton more than the element preceding it.
  • This is done so that elements end up in columns with other elements which have similar properties.
269
Q

What is a period and an example?

A
  • Period: These are the horizontal rows that show the number of shells of electrons an atom has and are numbered from 1 - 7.
  • E.g. elements in period 2 have two electron shells, elements in period 3 have three electron shells.
270
Q

What is a group? What is an example?

A
  • Group: These are the vertical columns that show how many outer electrons each atom has and are numbered from 1 – 7, with a final group called group 0 (instead of group 8).
  • E.g. group 4 elements have atoms with 4 electrons in the outermost shell, group 6 elements have atoms with 6 electrons in the outermost shell and so on.
271
Q

What does the group number indicate?

A
  • The group number of an element which is given on the Periodic Table indicates the number of electrons in the outer shell (valence electrons).
272
Q

What can we use the group number to do?

A
  • We can use the group number to predict how elements will react as the number of valence shell electrons in an element influences how the element reacts.
    Therefore, elements in the same group react similarly.
  • By observing the reaction of one element from a group, you can predict how the other elements in that group will react.
  • By reacting two or more elements from the same group and observing what happens in those reactions you can make predictions about reactivity and establish trends in reactivity in that group.
273
Q

What happens to the group 1 metals as you go down the group?

A

The group 1 metals become more reactive as you move down the group while the group 7 halides show a decrease in reactivity moving down the group.

274
Q

What does “periodic” mean?

A

The word “periodic” is used in the name of the Periodic Table as similar properties appear in elements placed at regular intervals throughout the table.

275
Q

What name is given to different atoms chemically bonded in a fixed ratio?

A

A compound.

Chemsitry (10 decks)

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