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Chemistry > Atomic Structure and the Periodic Table > Flashcards

Atomic Structure and the Periodic Table Flashcards

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1
Q

What is the radius of an atom?

A

0.1 nanometres (1 x 10^-10)

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2
Q

Describe the nucleus?

A

1) It’s in the middle of the atom
2) It contains protons and neutrons
3) It has a positive charge because of the protons
4) The nucleus has a radius of 1x10^-14 metres
5) Almost the whole mass of the atom is concentrated in the nucleus

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3
Q

Describe the electrons?

A

1) Move around the nucleus in electron shells
2) They are negatively charged and tiny but they cover a lot of space
3) The volume of their orbits determines the size of the atom
4) Electrons have virtually no mass

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4
Q

What is the mass of a proton, neutron and electron?

A

The mass of a proton = 1, neutron = 1 and electron = negligible

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5
Q

What is the charge of a proton, neutron and electron?

A

The charge of a proton = +1, neutron = 0 and electron = -1

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6
Q

Why do atoms have no charge overall?

A

The number of protons = the number of electrons
This means the charges cancel out

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7
Q

Why do ions have a charge?

A

The number of protons ≠ the number of electrons

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8
Q

What does the nuclear symbol of an atom show?

A

Its atomic number and mass number

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9
Q

What does the atomic number show?

A

How many protons there are

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10
Q

What does the mass number show?

A

The total of number of protons and neutrons in the atom

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11
Q

What is an element?

A

It is a substance made up of atoms that all have the same number of protons in their nucleus.

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12
Q

What are isotopes?

A

They are different forms of the same element - they have the same number of protons but a different number of neutrons.

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13
Q

What is the relative atomic mass?

A

An average mass taking into account the different masses and abundances of all the isotopes that make up the element.

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14
Q

What is the equation for the relative atomic mass?

A

relative atomic mass = (sum of (isotope abundance x isotope mass number)) ÷ sum of abundance of all the isotopes

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15
Q

What are compounds?

A

A pure substance made from more than one type of element chemically bonded together.

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16
Q

How can compounds be represented?

A

By formulas.

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17
Q

What is a mixture?

A

A mixture contains two or more substances not chemically combined together.

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18
Q

What are the ways of separating substances in a mixture?

A

1) Chromatography
2) Filtration
3) Crystallisation
4) Distillation
5) Magnetism
6) Manual Separation
7) Evaporation

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19
Q

Describe a method for chromatography?

A

1) Draw a line near the bottom of a sheet of filter paper (use a pencil to do this as pencil marks are insoluble and won’t dissolve in the solvent)
2) Add a spot of the ink to the line and place the sheet in a beaker of solvent (e.g. water)
3) The solvent used depends on what’s being tested. Some compounds dissolve well in water, but sometimes other solvents, like ethanol, are needed
4) Make sure the ink isn’t touching the solvent - you don’t want it to dissolve into it
5) Place a lid on top of the container to stop the solvent evaporating
6) The solvent seeps up the paper, carrying the ink with it
7) Each different dye in the ink will move up the paper at a different rate so the dyes will separate out. Each dye will form a spot in a different place - 1 spot per dye in the ink
8) If any of the dyes in the ink are insoluble in the solvent you’ve used, they’ll stay on the baseline
9) When the solvent has nearly reached the top of the paper, take the paper out of the beaker and leave it to dry
10) The end result is a pattern of spots called a chromatogram

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20
Q

What does filtration do?

A

It separates insoluble solids from liquids. Or can be used for purification if there are solid impurities in a liquid reaction mixture.

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21
Q

What does soluble and insoluble mean?

A

Insoluble: the solid cannot be dissolved in the liquid
Soluble: the solid can be dissolved in the liquid

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22
Q

What are two ways to separate soluble solids from solutions?

A

1) Evaporation
2) Crystallisation

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23
Q

How does evaporation separate soluble solids from solutions as a method?

A

1) Pour the solution into an evaporating dish.
2) Slowly heat the solution. The solvent will evaporate and the solution will get more concentrated. Eventually, crystals will start to form.
3) Keep heating the evaporating dish until all you have left are dry crystals.

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24
Q

What are the advantages and disadvantages of using the evaporation technique to separate soluble solids from solutions?

A

Advantages: Really quick
Disadvantages: Only can use this method if the salt doesn’t decompose (break down)

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25
Q

How does crystallisation separate soluble solids from solutions as a method?

A

1) Pour the solution into an evaporating dish and gently heat the solution. Some of the solvent will evaporate and the solution will get more concentrated.
2) Once some of the solvent has evaporated, or when you see crystals start to form (the point of crystallisation), remove the dish from the heat and leave the solution to cool.
3) The salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution.
4) Filter the crystals out of the solution and leave them in a warm place to dry. You could also use a drying oven or a desiccator.

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26
Q

What is rock salt?

A

A mixture of salt and sand.

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27
Q

What techniques can separate rock salt?

A

1) Filtration
2) Crystallisation

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28
Q

Why is rock salt easy to separate?

A

Salt = soluble compound
Sand = insoluble compound

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29
Q

Describe a method to separate rock salt?

A

1) Grind the mixture to make sure the salt crystals are small so will dissolve easily
2) Put the mixture in water and stir. The salt will dissolve, but the sand won’t
3) Filter the mixture. The grains if sand won’t fit through the tiny holes in the filter paper, so they collect on the paper instead. The salt passes through the filter paper as its part of the solution.
4) Evaporate the water from the salt so that it forms dry crystals.

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30
Q

What is simple distillation used for?

A

To separate the liquid from a solution.

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31
Q

Describe the method of simple distillation to separate out solutions?

A

1) Heat the solution. The part of the solution that has the lowest boiling point evaporates first.
2) The vapor then cools, condenses and is collected.
3) The rest of the solution is left behind in the flask.

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32
Q

Label a diagram for simple distillation and fractional distillation?

A

Check page.18

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33
Q

What does distillation often separate?

A

Seawater to get pure distilled water.

34
Q

What is the problem with distillation?

A

You can only separate substances with very different boiling points.

35
Q

What is fractional distillation used for?

A

To separate a mixture of liquids.

36
Q

How does one perform the method of fractional distillation?

A

1) Put you mixture in a flask and stick a fractionating column on top
2) Heat your mixture
3) The different liquids will have different boiling points so they will evaporate at different temperatures
4) The liquid with the lowest boiling point evaporates first - once the thermometer matches the boiling point of this liquid, it will reach the top of the column
5) The column is cooler at the top than at the bottom so they will only get part of the way up before condensing and running back down towards the flask
6) Once the first liquid has been collected, raise the temperature until the next one reaches the top

37
Q

Describe the history of the atom?

A

1) In the 19th century, John Dalton said atoms were solid spheres and that different spheres made up the different elements
2) In 1897, J J Thompson discovered neutrons and said atoms weren’t solid spheres but positively charged balls with negatively charged electrons embedded in them - this was known as the plum pudding model
3) In 1909, Ernest Rutherford and his student Ernest Marsden conducted the famous alpha particle scattering experiment - he created the nuclear model of the atom which showed most of the mass was concentrated in the centre of the atom in the positively charged nucleus and a cloud of negative electrons surrounds this nucleus so most of the atom was empty space
4) A cloud of negative electrons would mean it would be attracted to nucleus which would cause the atom to collapse - so in 1913 Niels Bohr proposed electrons orbit the nucleus in fixed shells with a fixed distance away from the nucleus
5) Further experiments by Rutherford showed that the nucleus could be divided into smaller particles which have the same charge as a hydrogen nucleus - these particles were named protons
6) 20 years after the acceptance of nuclei, James Chadwick carried out an experiment which provided evidence for neutral particles in the nucleus which are now called neutrons

38
Q

What was the alpha scattering experiment?

A
  • He did this by firing a beam of alpha particles at a thin gold foil
  • If the atom was like the plum pudding model it would have passed straight through or only be slightly deflected
  • However, the results were that most passed straight through the sheet, some were deflected more than expected, a few were deflected back the way they came
39
Q

Where are electrons located?

A

In the shells

40
Q

What are the shells in an atom also known as?

A

The energy levels.

41
Q

Where are the lowest energy levels in an atom?

A

These are the closest shells to the nucleus.

42
Q

How many electrons are allowed in the:
1st shell
2nd shell
3rd shell

A

1st = 2 electrons
2nd = 8 electrons
3rd = 8 electrons

43
Q

Do you know how to drawn electron configurations as diagrams?

A

Check pg. 20

44
Q

What is the electronic configuration for a sodium atom?

A

2.8.1

45
Q

When is an atom stable?

A

When they have a full outer shell. If is is not full this makes the atom want to react to fill it.

46
Q

Until recently, what were the two ways to categorise elements?

A

1) Their physical and chemical properties
2) Their atomic weight

47
Q

Before recently, how was the periodic table arranged?

A

The tables were not complete and some elements were in the wrong group as it was in order of their atomic weight as well as their properties not being taken into account.

48
Q

What did Dmitri Mendeleev do?

A

1) In 1869, he took 50 known elements and arranged them into his Table of Elements with various gaps
2) He put the elements mainly in order of atomic weight but did switch that order if the properties meant it should be changed - an example of this is with Tellurium and Iodine, iodine has a smaller atomic weight but is placed after tellurium as it has similar properties to the elements in that group
3) Gaps were left in the table to ensure elements with similar properties stayed in the same groups, some of these gaps indicated the existence of undiscovered elements - this allowed Mendeleev to predict what their properties might be (when they were found and fitted the pattern it helped confirm Mendeleev’s ideas) - an example is when Mendeleev made predictions about the chemical and physical properties of an element that he called ekasilicon which we know today as germanium

49
Q

How is the modern periodic table laid out?

A

In order of increasing atomic number. This means there are repeating patterns in the properties of the elements.

50
Q

Do you know the different parts of the periodic table and what they mean?

A

Check pg.22

51
Q

Elements with similar properties form what on the periodic table?

A

Columns. These are called groups.

52
Q

What does a group number represent?

A

The amount of electrons those elements have in their outer shell.

53
Q

What are the rows called in a periodic table?

A

Periods which represents the number of electron shells in an element.

54
Q

What metal ions form?

A

Positive ions when they react.

55
Q

What non-metal ions form?

A

Negative ions when they react.

56
Q

What happens to the outer shell if it is far away from the nucleus?

A

The electrons have a weaker attraction.

57
Q

What do all metals have?

A

Metallic bonding which causes them to have similar physical properties.

58
Q

What are some properties of metals?

A

1) They’re strong
2) They’re malleable
3) They can conduct heat and electricity
4) They have high melting and boiling points

59
Q

What are some properties of non-metals?

A

1) Dull looking
2) Brittle
3) Not always a solid at room temperature
4) Don’t normally conduct electricity
5) They often have a lower density

60
Q

What are the properties of transition metals?

A

1) Good conductors of heat and electricity
2) They are very dense
3) Strong
4) Shiny
5) They can have more than one ion - e.g. copper and cobalt
6) They are often coloured and so compounds that contain them are colourful - e.g. potassium chromate and potassium manganate
7) Often make good catalysts - e.g. nickel for hydrogenation of alkenes and iron for the Haber process for making ammonia

61
Q

What are the group 1 metals called?

A

The alkali metals.

62
Q

Why are the group 1 metals reactive?

A

They have only one electron in their outer shell.

63
Q

What are the properties for the alkali metals?

A

1) They are soft
2) They have a low density
3) They are very reactive

64
Q

What are the trends for the group 1 metals?

A
  • Increasing reactivity as you go down the column - outer electron is easily lost as the attraction between the nucleus and the electron decreases, because the electron is further away from the nucleus
  • Melting and boiling points decrease as you go down the column
  • The relative atomic mass increases as you go down the column
65
Q

How much energy do Group 1 metals need to become an ion? What does this result in?

A

They don’t need much energy. It is easy for them to loose their outer shell so this is why they only have react to form ionic compounds. And these compounds are generally white solids that dissolve in water to form a colourless solution.

66
Q

What is the reaction of Group 1 elements like in water?

A

They react vigorously, producing hydrogen gas and metal hydroxides (these are compounds that dissolve in water to produce alkaline solutions. The more reactive an alkali metal is the more violent of a reaction. The amount of energy given out by the reaction increases down the group (e.g. Potassium releases enough energy to ignite hydrogen).

67
Q

What is the equation of Group 1 metals reacting with water?

A

EXAMPLE OF EQUATION:

2Na(s) + 2H2O(l) —> 2NaOH(aq) + H2(g)

68
Q

What is the reaction of Group 1 elements with chlorine like?

A

Group 1 metals act vigorously when heated in chlorine gas to form white metal chloride salts. As you go down the group the reactivity increases so the reaction becomes more vigorous.

69
Q

What is the equation of Group 1 metals reacting with chlorine?

A

EXAMPLE OF EQUATION:

2Na(s) + Cl2(g) —-> 2NaCl(s)

70
Q

What is the reaction of Group 1 elements with oxygen like?

A

The Group 1 metals react with oxygen to form a metal oxide. Different types of oxide will form depending on the Group 1 metal:
* Lithium –> lithium oxide
* Sodium –> sodium oxide
* Potassium –> potassium oxide

71
Q

What are the Group 1 metals properties?

A

1) Group 1 metals are much more reactive than transition metals - they react more vigorously with water, oxygen or Group 7 elements, for example.
2) They are less dense, strong and hard than the transition metals and have much lower boiling points.

72
Q

What are the Group 7 elements known as?

A

The Halogens.

73
Q

What and describe the 4 halogens?

A

1) Fluorine - very reactive, poisonous yellow gas
2) Chlorine - fairly reactive, poisonous dense green gas
3) Bromine - dense, poisonous, red-brown volatile liquid
4) Iodine - dark grey crystalline solid or a purple vapour

74
Q

What is the structure of the halogens?

A

They are molecules which are pairs of atoms.

75
Q

What is the trend for the halogens?

A

As you go down Group 7 the halogens:
1) Become less reactive so this means that it’s harder to gain an extra electron because the outer shell’s further from the nucleus
2) Have a higher melting and boiling point
3) Have a higher relative atomic mass

76
Q

How can the halogens form molecular compounds?

A

Halogens can share electrons via covalent bonding with other non-metals to achieve a full outer shell. The compounds that form when halogens react with non-metals all have simple molecular structures.

77
Q

What do halogens form when they bond with metals?

A

Halides. The compounds that form have ionic structures.

78
Q

What is a displacement reaction?

A

It occurs between a more reactive halogen and the salt of a less reactive one (e.g. chlorine will displace bromine from an aqueous solution of its salt).

79
Q

Show an displacement reaction in an equation?

A

EXAMPLE EQUATION:

Cl2(g) + 2KBr —> Br2 + 2KCl

80
Q

What are the elements of Group 0 known as?

A

The noble gases.

81
Q

What are the facts of the noble gases?

A

1) They all have a full outer shell making them inert.
2) They exist as monatomic gases
3) They are all colourless gases at room temperature
4) They’re non-flammable
5) The boiling points of the noble gases increase as you move down the group - this is because of the number of electrons in each atom leading to greater intermolecular forces between them which need to be overcome
6) The relative atomic mass increases as you go down the group

Chemistry (6 decks)

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