GCSE CHEM (c1)

Name the models of the atom shown in above figure.(F)

A=plum pudding

B=Bohr

Compare model A with the model of the atom used today.

Use the figure above. (F)

(Plum pudding)

Similarities

• both contain electrons

• both are neutral overall

Differences

• model A has no nucleus

or

the model used today has a nucleus

• model A has no protons

or

the model used today has protons

• model A has no neutrons

or

the model used today has neutrons

• model A has positive charge spread throughout the atom

or

model A is a ball of positive charge

• the model used today has the positive charge in the centre

• model A the electrons are distributed randomly

• the model used today has electrons in shells / energy levels

• the mass was spread throughout model A

• the mass is concentrated at the centre of the model used today

• model A does not have empty space

Modem used today is mostly empty space

Chadwick’s experiments showed the existence of neutrons in an atom.

This led to an understanding of isotopes.

Define the term ‘isotopes’.

Refer to subatomic particles in your answer.(F)

atoms with the same number of protons

allow atoms of the same element

allow atoms with the same

atomic number

1

with different numbers of neutrons

Which particles have the same relative mass?(F)

a neutron and a proton

The formula of a compound is N2O

How many of each type of atom are in one molecule of N2O?(F)

nitrogen) 2 / two

(oxygen) 1 / one

An atom of element Z contains:

• 3 electrons

• 4 neutrons

• 3 protons.

(d) Give the name of element Z.

Use the periodic table.(F)

lithium

Describe the plum pudding model of the atom.(F)

a ball of positive charge

do not accept references to protons, nuclei,

neutrons

1

with (negative) electrons embedded

An atom of element Z contains:

• 3 electrons

• 4 neutrons

• 3 protons.

(d) Give the name of element Z.

Use the periodic table.(F)

lithium

Very few atoms of the element tennessine (Ts) have ever been identified.

The atomic number of tennessine is 117

(c) Predict the number of outer shell electrons in an atom of tennessine.

Give one reason for your answer.

Use the periodic table.

Number of outer shell electrons _______

Reason (F)

(number of outer shell electrons) 7

1

(reason) (tennessine is in) Group 7

1

Tennessine was first identified by a small group of scientists in 2010.

Suggest one reason why tennessine was not accepted as a new element by other

scientists until 2015.(F)

(time needed for) peer review

Calculate the relative atomic mass (Ar) of element R.

Give your answer to 1 decimal place.(F)

An atom of element Y has:

• an atomic number of 9

• a mass number of 19.

Give the number of electrons and the number of neutrons in this atom.(F)

number of electrons) 9

1

(number of neutrons) 10

Calculate the relative atomic mass (Ar) of element Z.(F)

Suggest the identity of element Z.(F)

potassium / K

Isotopes of the same element have different mass numbers because the isotopes

have different numbers of _______________.(F)

Neutrons

This question is about the periodic table.

Sodium and potassium are in Group 1 of the periodic table.

(a) Give one similarity and one difference between the electronic structures of sodium

and potassium.(F)

Similarity __________________________________________________________

___________________________________________________________________

Difference _________________________________________________________

___________________________________________________________________

(similarity)

both have one outer (shell)

electron

allow energy level for shell

allow same number of outer (shell) electrons

1

(difference)

sodium has 3 shells but

potassium has 4 shells

Group 1 elements react with water.

(b) Give two observations made when potassium reacts with water.(F)

any two from:

• effervescence / bubbles / fizzing

ignore gas produced

• (potassium) floats

• (potassium) moves around

• (potassium) becomes smaller

• (potassium) melts

allow (potassium) forms a ball

ignore colour of flame

• flame

• explosion

Potassium hydroxide solution is produced when potassium reacts with water.

What is the colour of universal indicator when added to potassium hydroxide

solution?

Give one reason for your answer.(F)

Colour of universal indicator _________________________________________

Reason __________________________________________________________

blue / violet / purple

(the solution is) alkaline

Estimate the density (X) of krypton.

Use the figure and table above.(F)

3.4

The elements in Group 7 are called the halogens.

A more reactive halogen can displace a less reactive halogen from a solution of its

salt.

Which combination of solutions will produce a reaction when mixed?(F)

chlorine and potassium bromide

Which of the following describes the trends going down Group 7?(F)

relative molecular mass increases and boiling point increases

The scientist left gaps in the periodic table in the figure above.

Each gap is represented by a question mark (?).

Give one reason why the scientist left gaps in this periodic table.(F)

for elements that had not been discovered (at that time)

allow for missing elements

or

so that elements with similar properties are grouped together

The modern periodic table is different from the periodic table in above figure.

One extra group of elements has been added.

What is the name of the extra group of elements in the modern periodic table?(F)

noble gases

Why do the elements in Group 1 of the modern periodic table have similar chemical

properties?(F)

the elements all have one electron in the outer shell

Predict value X.(F)

63 (°C)

allow a value in the range 49 to 88 (°C)

Give one observation you would see when a small piece of potassium is added to

water.(F)

any one from:

• floats

• moves (on the surface)

• melts

allow forms a ball

• fizzes / bubbles

• flame

F

This question is about elements in the periodic table.

(a) Argon has the atomic number 18

Explain why argon does not form compounds.

Answer in terms of electrons.(H)

(a) (atoms of) argon have a stable arrangement of electrons

allow (atoms of) argon have a full outer shell (of

electrons)

1

(so) argon (atoms) do not share / transfer electrons

Phosphorus (P) is the element below nitrogen in the periodic table.

Predict the formula of the compound formed between phosphorus and hydrogen.

Formula = _(H)

PH3

Tellurium is the element with atomic number 52

Predict whether tellurium reacts with metals.

Explain your answer.

Answer in terms of the position of tellurium in the periodic table.(H)

yes, because tellurium is towards the right of the periodic table

allow yes, because tellurium is in Group 6

1

(so) tellurium is a non-metal(1)

Or

yes, because tellurium is in the same group as oxygen / sulfur (1)

(and) oxygen / sulfur will react with metals (1)

Or

cannot predict as tellurium is towards the bottom and to the right of

the periodic table (1)

(so) don't know whether tellurium is a metal or non-metal (1)

Barium (Ba) is an element in Group 2 of the periodic table.

Barium reacts with hydrochloric acid.

(d) Suggest two observations that could be made when barium reacts with hydrochloric

acid.(H)

any two from:

• effervescence / fizzing / bubbles

ignore produces a gas

• barium disappears

allow barium gets smaller

• forms a colourless solution

• temperature increases

Write a balanced symbol equation for the reaction between barium and hydrochloric

acid.(H)

Ba + 2 HCl BaCl2 + H2

This question is about groups in the periodic table.

The elements in Group 1 become more reactive going down the group.

Rubidium is below potassium in Group 1.

(a) Rubidium and potassium are added to water.

Predict one observation you would see that shows that rubidium is more reactive

than potassium. (H)

any one from:

• more vigorous bubbling (for rubidium)

• bigger / brighter flame (for rubidium)

allow converse statements for potassium

allow (rubidium) catches fire more quickly

allow (rubidium) moves around more quickly

allow (rubidium) explodes

allow (rubidium) disappears more quickly

allow (rubidium) melts more quickly

Explain why rubidium is more reactive than potassium.(H)

(rubidium’s) outer shell / electron is further from the nucleus

allow the (rubidium) atom is larger

allow (rubidium) has more shells

1

(so) there is less (electrostatic) attraction between the nucleus and the

outer electron (in rubidium)

allow (so) there is more shielding between the outer electron

and the nucleus (in rubidium)

1

(so) the outer electron (in rubidium) is more easily lost

allow (so) less energy is needed to remove the (outer)

electron (in rubidium)

allow energy level for shell throughout

allow converse argument in terms of potassium

Complete the equation for the reaction of rubidium with water.

You should balance the equation.

Rb + H2O + (H) (3)

2 Rb + 2 H2O 2 RbOH + H2

The noble gases are in Group 0.

(d) Which is a correct statement about the noble gases?(H)

the noble gases have boiling points that increase going down the group

H

F

SECTIONS A B AND C

Which two of the following are typical properties of a transition metal? (chemistry

only)

can be bent and shaped

good conductor of electricity

F

1.B

2.A

This question is about metals.

(a) Platinum is used to make jewellery.

Suggest one reason why platinum is used to make jewellery. F

any one from:

• unreactive

allow does not react with air / water / skin

allow does not tarnish

• appearance

allow aesthetic reasons

• easily shaped

allow malleable

allow easily moulded

ignore references to cost

ignore references to hardness / strength

ignore references to melting / boiling point

Give two observations that could be seen when sodium is added to water. F

any two from:

• bubbles

• moves

• floats

• melts

allow forms a ball

• disappears

allow catches fire

(c) Copper is a transition element.

Sodium is a Group 1 element.

What are two differences between copper and sodium? (chemistry only) F

copper is harder

1

copper is less reactive

The metals aluminium and copper can be used to make pans for cooking.

The table below shows information about the two metals.

The higher the value for thermal conductivity, the better the metal conducts thermal

energy.

copper is the better conductor

• so heats food more quickly

• copper has the higher density

• so the pan is heavier

• copper costs more per kilogram

• so the pan is more expensive to buy

• simple judgement

Give two differences between the physical properties of the elements in Group 1

and those of the transition elements. (chemistry only) F

(Group 1 elements)

• have lower melting / boiling points

• have lower densities

• are less strong

• are softer

allow (Group 1 elements are) more malleable / ductile

allow (Group 1 elements) are not useful as catalysts

ignore transition elements form coloured compounds

ignore transition elements form ions with different charges

ignore references to chemical properties

allow converse statements for transition elements

Aluminium is a metal.

Describe how metals conduct electricity.

Answer in terms of electrons.

delocalised electrons

allow free electrons

1

(the electrons) carry (electrical) charge

ignore current / electricity for charge

1

(the electrons move) through the metal / aluminium / structure

Name the type of bonding in compounds formed between metals and non-metals.

ionic

Magnesium oxide is a compound formed from the metal magnesium and the

non-metal oxygen.

Describe what happens when a magnesium atom reacts with an oxygen atom.

You should refer to electrons in your answer. F

magnesium (atom) loses electrons

1

oxygen (atom) gains electrons

1

two electrons (are transferred)

1

magnesium ions and oxide ions are formed

This question is about elements, compounds and mixtures.

(a) Substance A contains only one type of atom.

Substance A does not conduct electricity.

Which type of substance is A?

non-metallic element

Substance B contains two types of atoms.

The atoms are chemically combined together in fixed proportions.

Which type of substance is B?

Compound

What is the name of the elements in Group 0 of the periodic table?

Noble gases

Which statement about the elements in Group 0 is correct?

the boiling points increase down the group

Neon is in Group 0.

What type of particles are in a sample of neon?

Atoms

XO2

Fine and coarse particles of the metallic element are also cubes.

The length of a fine particle cube is 10 times smaller than the length of a

coarse particle cube.

How does the surface area to volume ratio of the fine particle cube

compare with that of the coarse particle cube?

Tick (✓) one box.

the surface area to volume ratio of the fine particle is 10 times greater

This question is about atomic structure and the periodic table.

Gallium (Ga) is an element that has two isotopes.

(a) Give the meaning of ‘isotopes’

.

You should answer in terms of subatomic particles.

atoms with the) same number of protons

allow atoms with the same atomic

number

allow atoms of the same element

ignore the same number of electrons

1

(but with) different numbers of neutrons

Gallium (Ga) is in Group 3 of the modern periodic table.

(c) Give the numbers of electrons and neutrons in an atom of the isotope

69 on top

31 on bottom

number of electrons) = 31

(number of neutrons) = 38

What is the most likely formula of a gallium ion?

Ga3+

) Gallium was discovered six years after Mendeleev published his periodic

table.

Give two reasons why the discovery of gallium helped Mendeleev’s

periodic table to become accepted.

gallium) fitted in a gap (Mendeleev had left)

1

(gallium’s) properties were predicted correctly (by Mendeleev)

This question is about models of the atom.

(a) Atoms were first thought to be tiny spheres that could not be divided.

Which particle was discovered to change this model of the atom?

electron

A scientist fired particles at gold atoms.

Some of these particles were scattered.

The results led to a different model of the atom.

Which type of particle was fired at the gold atoms?

Alpha

Which scientist first suggested that electrons orbit the nucleus at specific

distances?

Bohr

Protons

Neutrons

Protons+neutrons

The radius of an atom is approximately 1 × 10–10 m

A teacher uses a ball of radius 1 cm to represent the nucleus.

What could represent the atom on the same scale?

a sports arena of radius 100 m

The plum pudding model did not have a nucleus.

Describe three other differences between the nuclear model of the atom

and the plum pudding model.

any three from: (nuclear model)

• mostly empty space

allow the plum pudding model has no

empty space

allow the plum pudding model is solid

• the positive charge is (all) in the nucleus

allow in the plum pudding model the

atom is a ball of positive charge (with

embedded electrons)

do not accept reference to protons

• the mass is concentrated in the nucleus

allow in the plum pudding model the

mass is spread out

do not accept reference to neutrons

• the electrons and the nucleus are separate

allow in the plum pudding model the

electrons are embedded

allow in the nuclear model the electrons are in

orbits

Niels Bohr adapted the nuclear model.

Describe the change that Bohr made to the nuclear model.

electrons orbit the nucleus

do not accept reference to protons /

neutrons

allow electrons are in energy levels

around the nucleus

or

allow electrons are in shells around the

nucleus

1

electrons are at specific distances from the nucleus

Mendeleev published his periodic table in 1869.

Mendeleev arranged the elements in order of atomic weight.

Mendeleev then reversed the order of some pairs of elements.

A student suggested Mendeleev’s reason for reversing the order was to

arrange the elements in order of atomic number.

Explain why the student’s suggestion cannot be correct.

Use the diagram above.

atomic number is the number of protons

1

(and) protons were not discovered until later

Give the correct reason why Mendeleev reversed the order of some pairs

of elements.

so their properties matched the rest of the group

Which particle has the lowest mass?

Electron

Define mass number

number of protons plus neutrons

Why is the mass number different in the two isotopes?

(the isotopes contain) different numbers of neutrons

The model of the atom changed as new evidence was discovered.

The plum pudding model suggested that the atom was a ball of positive

charge with electrons embedded in it.

Evidence from the alpha particle scattering experiment led to a change in

the model of the atom from the plum pudding model.

Explain how

most (alpha) particles passed (straight) through (the gold foil)

1

(so) the mass of the atom is concentrated in the nucleus / centre

or

(so) most of the atom is empty space

1

some (alpha) particles were deflected / reflected

1

(so) the atom has a (positively) charged nucleus / centre

What is a mixture of metals called?

an alloy

Why is the mixture of metals in Figure 2 harder than the pure metal?

the layers in the mixture are distorted

Element X has two isotopes. Their mass numbers are 69 and 71

The percentage abundance of each isotope is:

• 60% of 69X

• 40% of 71X

Estimate the relative atomic mass of element X.

between 69.5 and 70.0

Chadwick’s experimental work on the atom led to a better understanding of

isotopes.

Explain how his work led to this understanding.

Chadwick provided the evidence to show the existence of neutrons

allow Chadwick discovered neutrons

1

1

1

(this was necessary because) isotopes have the same number of

protons

allow (this was necessary because)

isotopes have the same atomic number

or

element

(this was necessary because) isotopes are atoms of the same

ignore isotopes have the same number

of electrons

but with different numbers of neutrons

allow but with different mass (numbers)

Name the particle in the atom discovered by James Chadwick.

Neutron

The plum pudding model of the atom was replaced by the nuclear model.

The nuclear model was developed after the alpha particle scattering

experiment.

Compare the plum pudding model with the nuclear model of the atom.

This question is about mixtures and analysis.

(a) Which two substances are mixtures?

Air

Steel

1. Pure substance in chemistry

Match: "A single element or a single compound" 

2. Pure substance in everyday life

Match: "A substance that has had nothing added to it" 

What is the test for chlorine gas?

Damp litmus paper turns white

Name the sub-atomic particles in part Z (nucleus) of a boron atom.

Give the relative charges of these sub-atomic particles.

Neutron 0

Electron -1

Proton +1

Explain what is wrong with the electronic structure shown in Figure 2.

too many electrons in the first energy level or inner shell

allow inner shell can only have a maximum of 2

electrons

too few electrons in the second energy level or outer shell

allow neon has 8 electrons in its outer shell or neon

does not have 1 electron in its outer shell

allow neon has a stable arrangement of electrons

or a full outer shell

1

1

1

1

1

neon does not have 9 electrons or neon has 10 electrons

Use Figure 2 to help you answer this question.

Describe, as fully as you can, what happens when sodium reacts

with fluorine to produce sodium fluoride.

sodium (atom) loses

fluorine (atom) gains

one electron

ions formed

Sodium fluoride is an ionic substance.

What are two properties of ionic substances?