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GCSE - Chemistry > Topic 1 - Key Concepts In Chemistry > Flashcards

Topic 1 - Key Concepts In Chemistry Flashcards

1
Q

What are the 3 ideas in John Daltons theory about the atom?

A
  1. Atoms cannot be created, divided or destroyed
  2. Atoms of same element are exactly the same/atoms of different elements are different
  3. 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

Discovery of subatomic particles

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3
Q

Describe structure of atom

A

Small central nucleus made up of protons and neutrons

Electrons orbit the nucleus in shells

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4
Q

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

A

Radius of nucleus is 1x10⁻¹⁴m

This is 1/10,000 of atomic radius

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5
Q

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

A

Proton 1
Neutron 1
Electron 1/1836

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6
Q

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

A

Proton +1
Neutron 0
Electron -1

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7
Q

Why do atoms contain equal numbers of protons and electrons

A

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

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8
Q

Where is the mass of an atom concentrated

A

In nucleus

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9
Q

What does atomic number of an atom represent

A

Number of protons

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10
Q

What does mass number of an atom mean

A

Mass number is number of protons and neutrons found in nucleus of atom

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11
Q

Atoms of same element have same number of ________ in nucleus and this is unique to that element

A

Protons

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12
Q

Whats an isotope

A

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

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13
Q

Boron has atomic number 5 and mass number 11. How many protons, neutrons and electrons does Boron have?

A

5 protons
5 electrons
6 neutrons

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14
Q

Why is relative atomic mass not always a whole number

A

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

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15
Q

What 2 values would be requires 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
  • Switched 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

Used properties of elements next to 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 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 elements arranged in the modern periodic table?

A

In order of increasing atomic number

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20
Q

Elements in the same group (column) have similar _______ ________

A

Chemical properties

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21
Q

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

A

Same no of outer shell electrons

No of outer shell electrons determines how atom reacts

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22
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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23
Q

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

A

All elements in same group have same number of outer shell electrons

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24
Q

On which side pf periodic table are metals positioned?

A

Left side

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25
What determines whether an element is a metal or non metal?
Atomic structure of the elements
26
Whats the max number pf electrons allowed in each of first three shells
1st shell - 2 | 2nd + 3rd shell - 8
27
When are atoms most stable
When they have full electron shells
28
The atomic number of Na is 11. | Whats the electronic configuration of Na?
2, 8, 1
29
How is electron configuration of an element related to its position in the periodic table?
Diagram: no of rings is period, no of electrons in outer ring is group, total no of electrons is atomic number Number: (eg sodium 2.8.1) sodium has three shells as there are 3 numbers, last number is no of outer shell electrons/group, sum of digits is atomic number
30
Whats an ionic bond?
A bond between a metal and non metal involving transfer of electrons
31
In terms of electrons, describe what happens to the metal and non metal when an ionic bond forms
Metal atom loses electrons to become a positively charged ion (cation) Non metal gains electrons to become a negatively charged ion (anion)
32
Whats an ion
An ion is an atom or group of atoms with a positive or negative charge
33
If an ion is positively charged, has it lost of gained electrons?
Lost. There are fewer negatively charged electrons to cancel out the charge of the positive protons so overall charge becomes positive.
34
Na⁺ has atomic no 11 and mass no 23. How many protons, neutrons and electrons are in this ion?
11 protons 10 electrons 12 neutrons
35
O²⁻ has atomic no 8 and mass no 16. How many protons, neutrons and electrons are in this ion?
8 protons 10 electrons 8 neutrons
36
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)
37
What type of ions do elements in group 1 and 2 form?
Cations (positive) Group 1 metals form 1+ ions Group 2 metals form 2+ ions
38
What type of ions do elements from groups 6 and 7 form?
Non metals so form anions (negative) Group 6 forms 2- ions Group 7 forms 1- ions
39
What does it mean if an ionic compound ends in -ide?
Compound contains 2 elements
40
What does it mean if an ionic compound ends in -ate?
The compound contains at least 3 elements, one of which is oxygen
41
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
42
Whats the chemical formula of sodium oxide, formed from Na⁺ and O²⁻ ?
Na₂O | Charges must balance so 2 sodium ions are required
43
Whats the chemical formula of magnesium hydroxide, formed from Mg²⁺ and OH⁻ ?
Mg(OH)₂ | Charges must balance so 2 hydroxide ions are required
44
What is a covalent bond?
A bond formed when an electron pair is shared between 2 atoms
45
What forms as a result of covalent bonding?
A molecule
46
True or false? ‘Covalent bonds are weak’
FALSE | Covalent bonds are strong
47
Which is smaller, an atom or a molecule?
An atom | Simple molecules consist of atoms joined by strong covalent bonds within the molecule
48
Why do ionic compounds have high melting points?
Strong electrostatic attraction between the positive and negative ions requires a lot of energy to overcome
49
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 cant move.
50
Why do simple molecular compounds have low melting and boiling points?
They have weak intermolecular forces (forces between molecules) which only require a little energy to overcome
51
Do simple molecular compounds conduct electricity? Why? Why not?
No because there are no charged particles
52
Do giant covalent structures have a high melting point? Explain your answer.
Yes because they have lots of strong covalent bonds which require a lot of energy to break
53
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.
54
True or false? ‘Metals are insoluble in water’
TRUE
55
Name two giant covalent structures formed from carbon atoms
Diamond | Graphite
56
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
57
Describe and explain the properties of graphite
Soft/slippery because of weak intermolecular forces between layers - allow to slide over each other Conducts electricity because theres one delocalised electron per carbon atom. These electrons are mobile charges
58
Describe structure of diamond
All carbon atoms are covalently bonded to 4 other carbon atoms No delocalised electrons
59
Describe properties of diamond
Very hard Very high melting pt Doesnt conduct electricity as are no charged particles
60
What are the uses of graphite? Why?
Electrodes because graphite conducts electricity and has high melting pt Lubricant because its slippery
61
Why is diamond used in cutting tools
Very hard
62
Whats a fullerene?
A molecule made of carbon, shaped like a closed tube or hollow ball
63
Name 2 fullerenes
Graphene | C₆₀ (buckminsterfullerene)
64
What are the properties of the fullerene C₆₀ ?
Slippery due to weak intermolecular forces Low melting pt Spherical Strong covalent bonds between carbon atoms in a molecule Large surface area
65
What are the properties of graphene?
High melting pt due to covalent bonding between carbon atoms | Conducts electricity because it has delocalised electrons
66
Why is graphene useful in electronics
Is extremely strong and has delocalised electrons - are free to move and carry charge One one atom thick as it is a single layer of graphite
67
What is a polymer? Name one
Long chain molecules formed from many monomers | Polyethene
68
What bond is formed between carbon atoms in polymer molecules?
Covalent bonds
69
What are the properties of metals?
``` High melting pt High density Good conductors of electricity Malleable and ductile Generally shiny ```
70
Explain why metals are malleable
Atoms are arranged in uniform rows which can slide over one another
71
Explain why metals can conduct electricity
Electrons in metal are charges that can move
72
What are the properties of non metals
Low boiling pt Poor conductors of electricity Brittle when solid
73
List the limitations of the following models when representing ionic compounds: dot and cross, 2D and 3D diagrams
Dot and cross- no lattice structure or ionic bonds 2D- only shows one layer, doesnt show formation of ions 3D- shows spaces between ions, doesnt show charges
74
List the limitations of the following models when representing covalent molecules: dot and cross and ball and stick
Dot and cross- doesnt show relative sizes of atoms or intermolecular forces Ball and stick- bonds shown as sticks rather than forces, doesnt show how covalent bonds form
75
How do you calculate the relative formula mass of a compound?
Add together all the relative atomic masses of the atoms in the compound
76
Whats the empirical formula? What 2 values could be used to calculate the empirical formula of a simple compound?
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
77
Whats the empirical formula for Fe₂O₄ ?
FeO₂
78
Whats the molecular formula?
Actual number of atoms of each element in a compound
79
Describe an experiment to work out the empirical formula of magnesium oxide
- weigh sample of magnesium - heat sample in crucible - weigh mass of magnesium oxide at end - calculate mass of oxygen - calculate moles of magnesium and oxygen using the experimental mass and relative atomic mass - work out whole number ratio to number of moles of magnesium to oxygen
80
What is the law of conservation of mass
No matter is lost or gained during a chemical reaction
81
If a reaction is carried out in a closed system, what can you say about the total mass od the reaction throughout the experiment?
Mass stays constant
82
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 gas escapes
83
52g of calcium reacts with oxygen to form 79g of calcium oxide. Using the law of conservation of mass, what mass of oxygen is needed?
79-52=27 | Mass of oxygen = 27g
84
What equation links mass, moles and relative atomic mass?
Mass (g) = moles x relative atomic mass (Mr)
85
How can you calculate concentration in g/dm³ ?
Concentration (g/dm³) = mass (g) / volume (dm³)
86
What is the avogadro constant?
Number of atoms, molecules or ions in one mole of a given substance Value of constant is 6.02 x 10²³
87
Whats the mass of 20 moles of calcium carbonate, CaCO₃
Mass (g) = moles x relative atomic mass (Mr) Mr = 100 20 x 100 = 2000g
88
What formula links the avogadro constant, moles and no of particles?
No of particles = avogadro constant x moles
89
How many atoms are in 3 moles of copper?
No of atoms = avogadro constant x moles 6. 02 x 10²³ x 3 1. 81 x 10²⁴
90
Whats a limiting reagent in a chemical reaction?
The chemical thats 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.

GCSE - Chemistry (8 decks)

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