Atomic structure + Periodic Table

Question 1

Give the meaning of ‘isotopes’. (2)

Answer 1

(atoms with the) same number of protons
(but with) different numbers of neutrons

Question 1

Which statement about the elements in Group 0 is correct?
Tick (✓) one box.
All elements in the group are very
reactive.

All elements in the group form negative ions.

The boiling points increase down the
group.

The relative atomic masses (Ar)
decrease down the group.

Answer 1

the boiling points increase down the group

Question 2

What is the most likely formula of a gallium ion?

Answer 2

Ga3+

Question 3

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.

Answer 3

(gallium) fitted in a gap (Mendeleev had left)

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

Question 4

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.

Answer 4

nuclear- mostly empty space
allow the plum pudding model has no empty space

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)

the mass is concentrated in the nucleus

the electrons and the nucleus are separate
allow in the plum pudding model the
electrons are embedded

Question 5

Describe the change that Bohr made to the nuclear model.

Answer 5

electrons orbit the nucleus
electrons are at specific distances from the nucleus

Question 6

Describe how the process of distillation shown in Figure 2 produces pure
water from salt solution.

Answer 6

solution is heated
* water evaporates
allow water boils / vaporises
* the vapour cools in the condenser
* the vapour condenses
or
the vapour turns to a liquid
* (pure) water collects in the beaker

Question 7

Define mass number.

Answer 7

number of protons plus neutrons

Question 8

Why is the mass number different in the two isotopes?

Answer 8

(the isotopes contain) different numbers of neutrons

Question 9

Evidence from the alpha particle scattering experiment led to a change in the model of the atom from the plum pudding model. Explain how. (4)

Answer 9

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

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

some (alpha) particles were deflected / reflected

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

Question 10

how to separate Ethanol from ethanol and water

Answer 10

Fractional distillation

Question 11

how to separate Salt from sea water

Answer 11

Crystallisation

Question 12

Chadwick’s experimental work on the atom led to a better understanding of
isotopes.
Explain how his work led to this understanding.

Answer 12

Chadwick provided the evidence to show the existence of neutrons

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

but with different numbers of neutrons

Question 13

This question is about mixtures and analysis.
(Which two substances are mixtures?
Tick two boxes.
-Air
-Carbon dioxide
-Graphite
-Sodium Chloride
-Steel

Answer 13

Air
Steel

Question 14

What is the test for chlorine gas

Answer 14

Damp litmus paper turns white

Question 15

What is always different for atoms of different elements?

Answer 15

number of protons

Question 16

Describe, as fully as you can, what happens when sodium reacts
with fluorine to produce sodium fluoride.

Answer 16

sodium (atom) loses

fluorine (atom) gains

one electron

ions formed

Question 17

Why does pure water not conduct electricity?

Answer 17

no delocalised / free electrons

Question 18

Explain why the reactivity of elements changes going down Group 1.

Answer 18

reactivity increases (going down the group)

(because) the outer electron / shell is further from the nucleus

(so) there is less attraction between the nucleus and the outer
electron / shell

(so) the atom loses an electron more easily

Question 19

Going down Group 7 the melting points _______________

Answer 19

increase

Question 20

Explain the trend in boiling points of the halogens shown in Table 1.

Answer 20

boiling point) increases (down the table / group)

(because) the relative formula / molecular mass increases

(so) the intermolecular forces increase (in strength)

(so) more energy is needed to overcome the intermolecular forces

Question 21

Why did Mendeleev’s periodic table become more widely accepted than
previous versions?

Answer 21

Mendeleev had predicted properties of missing elements

elements were discovered (that filled the spaces / gaps)

properties (of these elements) matched Mendeleev’s predictions

Question 22

Sodium is in Group 1 of the modern periodic table.
Describe what you would see when sodium reacts with chlorine.

Answer 22

-flame
-(white) solid forms
- colour of gas / chlorine disappears / fades

Question 23

Evaluate Newlands’ and Mendeleev’s tables.
You should include:
* a comparison of the tables
* reasons why Mendeleev’s table was more acceptable.

Answer 23

comparative points
*both tables have more than one element in a box
both have similar elements in the same column
*both are missing the noble gases
*both arranged elements in order of atomic weight

Newlands did not leave gaps for undiscovered elements
*Newlands had many more dissimilar elements in a column
Mendeleev left gaps for undiscovered elements
*Mendeleev changed the order of some elements

*Mendeleev predicted properties of missing elements
elements with properties predicted by Mendeleev were discovered
Mendeleev’s predictions turned out to be correct
elements were discovered which fitted the gaps

Question 24

Give one limitation of using a dot and cross diagram to represent an
ammonia molecule.

Answer 24

does not show the shape
or
only two-dimensional

Question 25

Suggest why the reaction in Stage 2 is carried out in an atmosphere of
argon and not in air.

Answer 25

argon is unreactive / inert

oxygen (from air) would react with sodium / titanium

Question 26

compare the
chemical and physical properties of transition elements and Group 1
elements.

Answer 26

Physical
Transition elements
* high melting points
* high densities
* strong
* hard
Group 1
* low melting points
* low densities
* soft
Chemical
Transition elements
* low reactivity / react slowly (with water or oxygen)
* used as catalysts
* ions with different charges
* coloured compounds
Group 1
* very reactive / react (quickly) with water / non-metals
* not used as catalysts
* white / colourless compounds
* only forms a +1 ion

Question 27

How can you tell that a chemical reaction is taking place?

Answer 27

there was a flame
* energy was given out
* a new substance was formed

Question 28

Give one disadvantage of using nanoparticles in sun creams.

Answer 28

• Potential cell damage to the body
• Harmful effects on the environment

Question 29

A student tested a metal chloride solution with sodium hydroxide solution.
A brown precipitate formed.
What was the metal ion in the metal chloride solution?

Answer 29

Iron(III)

Question 30

Explain why octane is a hydrocarbon.

Answer 30

contains hydrogen and carbon

(hydrogen and carbon) only

Question 31

Explain how a covalent bond holds two atoms together.

Answer 31

electrostatic force of attraction between shared pair of negatively charged electrons

and both positively charged nuclei

Question 32

Would collecting and plotting data for more sizes of nanoparticles improve the
conclusions?

Answer 32

(no) because trend / conclusion is already clear