The periodic table

Question 1

What characteristics are seen down the periodic table?

Answer 1

Increasing radius, higher energy orbitals, increasing shielding and decreasing ionisation energy.

Question 2

What characteristics are seen across the periodic table?

Answer 2

Increasing nuclear charge, similar radius, increasing ionisation energy.

Question 3

What characteristics are seen diagonally down the periodic table?

Answer 3

Increasing ionisation energy and electronegativity.

Question 4

How does the melting point of elements change down the periodic table?

Answer 4

Decrease down group one, increase down group seven, increase across a period up to group four and then drop sharply as elements form diatomic molecules held by weak intermolecular forces.

Question 5

What are redox reactions?

Answer 5

Processes where both reduction and oxidation occur.

Question 6

What is the difference between oxidation and reduction?

Answer 6

A species is oxidised if it loses electrons and reduced if it gains them.

Question 7

What is the difference between an oxidising and reducing agent?

Answer 7

A reducing agent gives and electron to another species and is oxidised. An oxidising agent removes an electron from another species and is reduced.

Question 8

Describe the group one elements reactions with water

Answer 8

Lithium- floats, fizzes and dissolves
Sodium- floats, fizzes, whizzes and dissolves
Potassium- floats, fizzes, explodes lilac flames

Question 9

What are the flame colours?

Answer 9

Barium- apple green
Calcium- brick red
Potassium- lilac
Sodium- yellow
Lithium- red

Question 10

What are the halogen precipitate colours?

Answer 10

Chloride- white precipitate
Bromide- cream precipitate
Iodide- yellow precipitate

Question 11

Describe the appearance of the halogens

Answer 11

Fluorine- pale yellow gas
Chlorine- pale green gas
Bromine- brown liquid
Iodine- grey black solid

Question 12

What is the general trend with group one elements?

Answer 12

Reactivity increases down the group and elements are more reactive than the group two elements, all soluble.

Question 13

What is the general trend with group two elements?

Answer 13

Solubility increases down the group.

Question 14

What is an electronegative element?

Answer 14

One having a strong affinity for an electron and thus acting as an oxidising agent.

Question 15

What is the general trend with group seven elements (halogens)?

Answer 15

Melting points increase down the group, volatility decreases down the group, reactivity decreases down the group.

Question 16

How is chlorine used in water treatment?

Answer 16

Water is treated with chlorine gas to make it safe to drink by killing typhoid and cholera bacteria.

Question 17

How is fluorine used in water treatment?

Answer 17

Fluorine is added to toothpaste and sometimes water to prevent tooth decay and strengthen bones to reduce osteoporosis.

Question 18

State a basic oxide

Answer 18

MgO or CaO.

Question 19

State an acidic oxide

Answer 19

SO2 or NO2.

Question 20

Where on the periodic table are basic oxides found?

Answer 20

The left hand side, with the bottom of the s block being most basic.

Question 21

Where on the periodic table are acidic oxides found?

Answer 21

The right hand side, especially the upper parts of groups 5 and 6.

Question 22

Why does ionisation energy increase across a group?

Answer 22

As there is a steady increase in the number of protons in the nucleus while the electron is in the same orbital and electron shielding isn’t increased much.

Question 23

Why does ionisation energy decrease down a period?

Answer 23

As the outer electron is further from the nucleus due to more shells so the effective nuclear charge decreases.

Question 24

What is meant by a displacement reaction in the halogens?

Answer 24

Reactions in which one halogen exchanges places with another halogen in a halide.

Question 25

Why do displacement reactions occur with halogens?

Answer 25

Halogens higher in the periodic table are stronger oxidising agents and thus remove an electron from the halide to liberate the free halogen while being reduced to the halide.

Question 26

Give the colours of the precipitates formed when sodium hydroxide is added to solutions containing metal ions

Answer 26

Mg2+ -white precipitate
Fe2+ -dark green precipitate
Cr3+ - grey green precipitate
Pb2+ - white precipitate

Question 27

Describe halogens reacting with iron

Answer 27

Iodine- Strong heating required, slow reaction with brown residue.
Bromine- Little heat needed, quick reaction with dark vapours.
Chlorine- Violent reaction, iron ignites pale green vapours.

Question 28

Why is chlorine the strongest oxidising agent?

Answer 28

It has the smallest radius with the nucleus closest to the outer shell, so it has the strongest attraction to electrons.

Question 29

What are the solubility trends for sulphates?

Answer 29

Mg- soluble
Ca- insoluble (cloudy ppt)
Sr- insoluble (lighter ppt)
Ba- insoluble (heavy ppt)

Question 30

What are the solubility trends for hydroxides?

Answer 30

Mg- insoluble
Ca- less insoluble
Sr- lesser insoluble
Ba- soluble

Question 31

What are the solubility trends for carbonates?

Answer 31

All insoluble.

Question 32

What is the test for sulphates?

Answer 32

Hydrochloric acid then Barium chloride, observation will be a white precipitate.

Question 33

How to identify carbonates?

Answer 33

Add acids to carbonate, bubbles of CO2 should be produced (CASWC).