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Separate Chemistry Edexcel GCSE > Topic 1 - Key Concepts > Flashcards

Topic 1 - Key Concepts Flashcards

1
Q

What are 3 ideas in John Dalton’s theory about the atom?

A
  • Atoms cannot be created 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 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 a 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 bounces 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 ( move around ) the nucleus in shells

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8
Q

What is the radius of the nucleus? How large is it compared to the radius atom?

A

The radius is 1x10^-14 m

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9
Q

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

A

Proton : 1
Neutron : 1
Electron : 1/200

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10
Q

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

A

Proton : +1
Neutron : 0
Electron: -1

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11
Q

Why do atoms contain equal numbers of protons and electrons?

A

Atoms are stable with no overall charge
Protons are positive and electrons are negative. The number must be equal so the charges balance

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12
Q

Where is the mass of an atom concentrated ?

A

In the nucleus

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13
Q

What does the atomic number represent?

A

The number of protons

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14
Q

What does the mass number mean?

A

Number of protons and neutrons found in the nucleus of an atoms

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15
Q

Atoms of the same element have the same number of ——— in the nucleus and that is unique to that element

A

Protons

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16
Q

What is an isotope?

A

Atom with the same number of protons but a different number of neutrons.
Isotopes of an element have the same atomic number but different mass numbers

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17
Q

Why is the relative atomic mass not always a whole number?

A

Different isotopes of the same element have different mass numbers. The relative atomic mass is an average of the masses of all of these isotopes

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18
Q

What 2 values would be required to calculate the relative atomic mass of chlorine?

A

Mass number and relative abundance of all of the isotopes of chlorine

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19
Q

How did Mendeleev arrange the elements in his periodic table?

A

Arranged with increasing atomic masses
Elements with similar properties put into groups
Switched the position of some elements
Gaps left for undiscovered elements

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20
Q

How could Mendeleev predict the properties of new elements?

A

He used the properties of elements next to these gaps to predict properties of undiscovered elements

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21
Q

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

A

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

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22
Q

How are elements arranged now?

A

In order of increasing atomic number

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23
Q

Elements in the same group have similar ————— —————-

A

Chemical properties

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24
Q

Why do elements in the same group 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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25
What does the period number tell you about all the elements in that period?
Elements in the same period have the same number of electron shells All elements in the period4 have 4 shells of electrons
26
What does the group number tell you about all the elements in that group?
All elements in the same group have the same number of outer electrons
27
On which side of the periodic table are the metals positioned?
Left hand side
28
What determines whether an element is a metal or non-metal ?
Atomic structures of the elements
29
What is the maximum number of electrons allowed in the first 3 shells?
1 st shell = 2 2 nd shell = 8 3 rd shell = 8
30
When are atoms most stable?
When they have a full outer shell
31
What is an ionic bond?
A bond between a metal and a non-metal involving the transfer of electrons
32
In terms of electrons, what happens to the metal and non metal when an ionic bond forms?
The metal atoms loses electrons to become a positively charged ion ( cation ) The non metal atom gains electrons to become a negatively charged ion ( anion )
33
What is an ion?
An ion is an atom or group of atoms with a positive or negative charge
34
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 change becomes positive
35
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 gasses
36
What type of ions do elements in group 1 and 2 form?
Cations - positive
37
What type of ions do elements in group 6 and 7 form?
They form anions - negative
38
What does it mean if an ionic compound ends in -ide?
The compound contains 2 elements
39
What does it mean if an ionic compound ends in - ate?
The compound contains at least 3 elements including oxygen
40
Describe the structure of an ionic compound?
Lattice structure Regular arrangement of ions Ions held together by strong electrostatic forces between ions with opposite charges
41
What is the chemical formula of sodium oxide?
Na2O Charges must balance so 2 sodium ions are required
42
What is the chemical formula of magnesium hydroxide?
Mg(OH)2
43
What is a covalent bond?
A bond formed when an electron pair is shared between two atoms
44
What forms as a result of covalent bonding?
A molecule
45
True or false? Covalent bonds are weak
False Covalent bonds are strong
46
Which is smaller, an atom or a molecule?
An atom. Simple molecules consist of atoms joined by strong covalent bonds within the molecule
47
Why do ionic compounds have high melting points ?
Strong electrostatic attraction between the positive and negative ions requires a lot of energy to overcome
48
When do ionic compounds 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.
49
Why do simple molecular compounds have low melting and boiling points?
They have weak intermolecular forced which only require a little energy
50
Do simple molecular compounds conduct electricity? Why/ why not?
No because there are no charged particles.
51
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.
52
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
53
True or false? Metals are insoluble in water
True
54
Name 2 giant covalent structures formed from carbon atoms
Graphite Diamond
55
Describe the structure of 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
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 atoms are covalently bonded to 4 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?
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 is fullerene ?
A molecule made of carbon, shaped like a closed tube or hollow ball.
62
Name 2 fullerenes
Graphene Buckminsterfullerene
63
What are the properties of C60 - buckminsterfullerene
Slippery due to weak intermolecular forces. Low melting point Spherical Strong covalent bonds between carbon atoms ina molecule Large surface area
64
What are the properties of graphene
High melting point due to covalent bonding between carbon atoms Conducts electricity because it has delocalised electrons
65
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
66
What is a polymer? Name a polymer?
Long chain molecules formed from many monomers Poly ethene
67
What bond is formed between carbon atoms in polymer molecules?
Covalent bonds
68
What are the properties of metal?
High melting point High density Good conductors of electricity Malleable and ductile Generally shiny
69
Explain why metals are malleable
The atoms are arranged in uniform rows which can slide over one another .
70
Explain why metals can conduct electricity
The electrons in the metal are charges that can move
71
What are the properties of non metals
Low boiling points Poor conductors of electricity Brittle when solid
72
List the limitations of the following models Dot and cross 2D diagrams 3D diagrams
Dot and cross : no lattice structures or ionic bonds 2D diagrams : only show one layer, doesn’t show the for,action of ions 3D diagrams : shows spaces between the ions, doesn’t show charges
73
List the limitations of the following models when representing covalent molecules Dot and cross Ball and stick
Dot and cross : doesn’t show relative sizes of atoms or intermolecular forces Ball and stick : bonds shown as sticks rather than forces , doesn’t show how covalent bonds are formed
74
How do you calculate the relative formula mass of a compound?
Add together all the relative atomic masses of the atoms in the compound
75
What is the empirical formula? What 2 values could be used to calculate the empirical formula of a simple compound?
The empirical formula is the smallest whole number ratio of the atoms of each element in a compound. Reacting masses or percentage composition can be used to calculate the empirical formula
76
What is the empirical formula for Fe2O4
FeO2
77
What is the molecular formula?
Actual number of atoms of each element in a compound
78
Describe an experiment to work out the empirical formula of magnesium oxide
- Weigh a sample of magnesium - Heat the sample in a crucible - Weigh the mass of magnesium oxide at the end - Calculate the mass of oxygen ( this is the increase of mass) - calculate the moles of magnesium and oxygen using the experimental mass and relative atomic mass. - work out the whole number ratio of moles of magnesium to oxygen
79
What is the law of the conservation of mass?
No matter is lost or gained during a chemical reaction
80
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
81
If a reaction is carried out in an open flask and gas is produces, what can you say about the total mass of the reaction?
Mass decreases, gas escapes
82
52g of calcium reacts with oxygen to form 79g of calcium oxide. What mass of oxygen is needed?
27 g
83
What equation links mass, moles and relative atomic mass?
Mass = moles x relative atomic mass
84
How can you calculate concentration in g/dm 3 ?
Concentration = mass / volume
85
What is the Avogadro constant ?
The number of atoms, molecules or ions in one mole of a given substance. 6.02 x 10 ^23
86
What is the mass of 20 moles of calcium carbonate , CaCO3 ?
Mass = moles x relative atomic mass Mr = 100 20 x 100 = 2000g
87
What formula links the Avogadro constant, moles and number of particles ?
Number of particles = Avogadro constant x moles
88
How many atoms are in 3 moles of copper?
Number of atoms = Avogadro’s constant x moles = 6.02 x 10^23 x 3 = 1.81 x 10^24
89
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, the excess of one of the reactants is used to ensure that the other reactant is completely used up.

Separate Chemistry Edexcel GCSE (3 decks)

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