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C1: Key Concepts In Chemistry Flashcards

1
Q

What are the three ideas in John Dalton’s theory about the atom?

A
  • Atoms cannot be created, divided or destroyed.
  • Atoms of the same element are exactly the same and atoms of different elements are different.
  • Atoms join with other atoms to make new substances.
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2
Q

What discovery caused the original dalton model of an atom to change?

A

The discovery of the subatomic particles

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3
Q

How did JJ Thomson discover the electron?

A

Thomson experimented with a cathode ray tube.
The beam moved towards the positively charged plate so he knew that the particles must have a negative charge.

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4
Q

Describe the atomic model proposed by JJ Thomson?

A

Plum pudding model.
Negatively charged electrons scattered through a positively charged material.

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5
Q

What did Ernest Rutherford discover from his gold foil experiment?

A

He shot a beam of positively charged particles at sheet of gold foil.
- Most of the particles passed straight through suggesting that atoms were mostly empty space.
- A few particles were deflected and a few bounced directly back showing that there must be a tiny, dense and positively-charged nucleus.

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6
Q

Describe Rutherford’s new model of the atom?

A
  • Mass is concentrated in the central nucleus.
  • Mostly empty space.
  • Electrons travel in random paths around the nucleus.
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7
Q

Describe the structure of an atom ?

A

Small central nucleus made up of protons and neutrons.

Electrons orbit the nucleus in shells.

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8
Q

What are the relative masses of protons, neutrons and electrons?

A

Proton: 1
Neutron: 1
Electron: 1/1836

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9
Q

What are the relative charges of protons neutrons and electrons?

A

Protons: +1
Neutrons: 0
Electrons: -1

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10
Q

Why do atoms contain equal numbers of protons and electrons?

A

Atoms are stable with no overall charge.
Protons are positively charged and electrons are negatively charged. For the charges to balance, the number of protons and electrons must be equal.

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11
Q

Where is the mass of an atom concentrated?

A

In the nucleus

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12
Q

What does the atomic number of an atom represent?

A

The number of protons

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13
Q

What does the mass number of an atom mean ?

A

The mass number is the number of protons and neutrons found in the nucleus of the atom

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14
Q

What is an isotope?

A

Atoms with the same number of protons (so they are the same element) but have different numbers of neutrons

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15
Q

What two values would be required to calculate the relative atomic mass of chlorine?

A

Mass numbers and relative abundances of all the isotopes of chlorine.

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16
Q

How did Mendeleev arrange the elements in his periodic table?

A

Elements arranged with increasing atomic masses.
Elements with similar properties put into groups (due to periodic trends in chemical properties).
Switched the position of some elements.
Gaps left for undiscovered elements.

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17
Q

How was Mendeleev able to predict the properties of new elements ?

A

He left gaps in his periodic table.
He used the properties of elements next to these gaps to predict properties of undiscovered elements

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18
Q

Mendeleev’s table lacked some amount of accuracy in the way he’d ordered his elements. Why was this?

A

Isotopes were poorly understood at the time.
Protons and neutrons had not yet been discovered.

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19
Q

How are the elements arranged in the modern periodic table?

A

In order of increasing atomic number

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20
Q

Why do elements in the same column have similar chemical properties?

A

Same number of outer shell electrons.
Number of outer shell electrons determines how an atom reacts.

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21
Q

What does the period (row) number tell you about all the elements in that period?

A

Elements in the same period have the same number of electron shells.

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22
Q

What does group (column) number tell you about all the elements in that group?

A

All elements in the same group have the same number of outer electrons.

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23
Q

Which side of the periodic table are the metals positioned?

A

Left hand side

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24
Q

What is the maximum number of electrons allowed in each of the shells?

A

1st shell: 2
2nd shell+ : 8

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25
When are atoms most stable ?
When they have a full electrons shells
26
What is an ionic bond ?
A bond between a metal and a non metal involving the transfer of electrons
27
In terms of electrons, describe what happens to the metal and non-metal when an ionic bond forms?
The metal atom loses electrons to become a positively charged ion (cation). The non-metal gains electrons to become a negatively charged ion (anion).
28
What is an ion?
An ion is an atom or group of atoms with a positive or negative charge
29
If an ion is positively charged, has it lost or gained electrons?
It has lost electrons. There are fewer negatively charged electrons to cancel out the charge of the positive protons. This means the overall charge becomes positive.
30
Why do elements in groups 1, 2, 6 and 7 readily form ions?
So they become more stable and achieve the electron structure of the noble gases (group 8).
31
What type of ions do elements in group 1 and 2 form?
Cations (positive) - Group 1 metals will form 1+ ions - Group 2 metals will form 2+ ions
32
What type of ions do elements in groups 6 and 7 form?
They are non-metals so form anions (negative) - Group 6 will form 2- ions - Group 7 will form 1- ions
33
What does it mean if an ionic compound ends in -ide?
The compound contains 2 elements.
34
What does it mean if an ionic compound ends in -ate?
The compound contains at least three elements, one of which is oxygen.
35
Describe the structure of an ionic compound?
Lattice structure. Regular arrangement of ions. lons held together by strong electrostatic forces between ions with opposite charges.
36
What is a covalent bond ?
A bond formed when an electron pair is shared between 2 atoms
37
What forms as a result of covalent bonds?
A molecule
38
True or false? Covalent bonds are weak?
FALSE covalent bonds are strong
39
Which is smaller, an atom or a molecule?
An atom. Simple molecules consist of atoms joined by strong covalent bonds within the molecule
40
Why do ionic compounds have high melting points?
Strong electrostatic attraction between the positive and negative ions requires a lot of energy to overcome.
41
When do ionic compounds conduct electricity? Why?
When molten or aqueous (dissolved in water) because the ions are charged and free to move. When solid, the ions are fixed in an ionic lattice so can't move.
42
Why do simple molecular compounds have a low melting and boiling points?
They have weak intermolecular forces which only require a little energy to break
43
Do simple molecular compounds conduct electricity?
No because there are no charged particles.
44
Do giant covalent structures have a high melting point?
Yes because they have lots of strong covalent bonds which require a lot of energy to break
45
How do metals conduct electricity and heat?
The positive ions are fixed in a sea of delocalised electrons. These electrons are free to move and carry charge/energy
46
True or False ? ‘Metals are insoluble in water’
True
47
Name 2 giant covalent structures formed from carbon atoms?
Graphite and Diamond
48
Describe the structure and properties relating to graphite?
Each carbon atom bonded to 3 other carbon atoms. Layers of hexagonal rings of carbon atoms. Weak intermolecular forces between layers. One delocalised electron per carbon atom.
49
Describe and explain the properties of graphite?
Graphite is soft / slippery because there are only weak intermolecular forces between layers which allow the layers to slide over one another. Graphite conducts electricity because there is one delocalised electron per carbon atom. The delocalised electrons are mobile charges.
50
Describe the structure of diamond?
All carbon atom are covalently bonded to four other carbon atoms. No delocalised electrons.
51
Describe the properties of diamond?
Very hard. Very high melting point. Doesn't conduct electricity as there are no charged particles.
52
What are the uses of graphite? Why?
Electrodes because graphite conducts electricity and has a high melting point. Lubricant because it's slippery (the layers in graphite can slide over each other).
53
Why is diamond
54
Name 2 giant covalent structures formed from carbon atoms?
Graphite Diamond
55
Describe the structure and properties relating to graphite?
Each carbon atom bonded to 3 other carbon atoms. Layers of hexagonal rings of carbon atoms. Weak intermolecular forces between layers. One delocalised electron per carbon atom.
56
Describe and explain the properties of graphite?
Graphite is soft / slippery because there are only weak intermolecular forces between layers which allow the layers to slide over one another. Graphite conducts electricity because there is one delocalised electron per carbon atom. The delocalised electrons are mobile charges.
57
Describe the structure of diamond?
All carbon atom are covalently bonded to four other carbon atoms. No delocalised electrons.
58
Describe the properties of diamond?
Very hard Very high melting point Doesn’t conduct electricity as there are no charged particles
59
What are the uses of graphite? Why?
Electrodes because graphite conducts electricity and has a high melting point. Lubricant because it's slippery (the layers in graphite can slide over each other).
60
Why is diamond used in cutting tools?
It’s very hard
61
What are the properties of graphene?
- High melting point due to covalent bonding between carbon atoms. - Conducts electricity because it has delocalised electrons.
62
Why is diamond used in cutting tools?
It’s very hard
63
What are the properties of graphene?
- High melting point due to covalent bonding between carbon atoms. - Conducts electricity because it has delocalised electrons.
64
Why is graphene useful in electronics?
It is extremely strong and has delocalised electrons which are free to move and carry charge. It is only one atom thick as it is a single layer of graphite.
65
What is a polymer? Name a polymer
Long chain molecules formed from many monomers. E.g. poly(ethene)
66
What bond is formed between carbon atoms in polymer molecules?
Covalent bonds
67
What are the properties of metals?
- High melting point. - High density. - Good conductors of electricity. - Malleable and ductile. - Generally shiny.
68
Explain why metals are malleable?
The atoms are arranged in uniform rows which can slide over one another.
69
Explain why metals can conduct electricity?
The electrons in the metal are charges that can move.
70
What are the general properties of non-metals?
- Low boiling points. - Poor conductors of electricity. - Brittle when solid.
71
How do you calculate the relative formula mass of a compound?
Add together all the relative atomic masses of the atoms in the compound.
72
What is the empirical formula?
• The empirical formula is the smallest whole number ratio of the atoms of each element in a compound.
73
What 2 values could be used to calculate the empirical formula of a simple compound?
• Reacting masses or percentage composition can be used to calculate the empirical formula.
74
What is the molecular formula?
Actual number of atoms of each element in a compound.
75
What is the law of conservation of mass?
No matter is lost or gained during a chemical reaction.
76
If a reaction is carried out in a closed system, what can you say about the total mass of the reaction throughout the experiment?
Mass stays constant.
77
If a reaction is carried out in an open flask and a gas is produced, what can you say about the total mass of the reaction throughout the experiment?
Mass decreases as the gas escapes.
78
79
What is a limiting reagent in a chemical reaction?
The chemical that is used up first in a reaction, preventing the formation of more product. Typically, an excess of one of reactants is used to ensure that the other reactant is completely used up.

Chemistry (11 decks)

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