Structure 3.1

Question 1

Periodicity

Answer 1

When arranged, there is a repeating pattern in the chemical and physical properties

Question 2

Atomic radius

Answer 2

Half the distance between two neighbouring nuclei

Question 3

Trend across a period

Answer 3

Nuclear charge increases, increase in electrostatic attraction, decrease in radius as electrons are pulled in

Question 4

Trend down a group

Answer 4

Number of occupied electron shells increases, increase in atomic radii.

Question 5

Isoelectric positive ions

Answer 5

Decrease in size across a period as electrons remains constant, but nuclear charge increases

Question 6

Isoelectric negative ions

Answer 6

Decrease in size across a period as electrons remain constant but nuclear charge increases

Question 7

Positive ions are smaller or larger than parent ions

Answer 7

Smaller (loss of outer energy level)

Question 8

Negative ions are smaller or larger than parent ions

Answer 8

Larger (addition of electron = increased electron repulsion = increased radius)

Question 9

Ionisation energy

Answer 9

Enthalpy change when an electron is removed from an atom in the gaseous state

Question 10

IE across a period

Answer 10

Increases due to the increase in nuclear charge leading to greater electrostatic attraction

Question 11

IE down a group

Answer 11

Nuclear charge increases but the shielding means it is about the same, so increased distance between electron and nucleus reduces attraction so decreases

Question 12

Electron affinity

Answer 12

Enthalpy change when an electron is added to an atom in the gaseous state (exothermic)

Question 13

Are second and third electron affinity exo or endo?

Answer 13

Endothermic as electron is repelled from the negative ion and needs to have energy to be added

Question 14

Electron affinity trends

Answer 14

Increases across a period and up a group - this is rough rule

Question 15

Electronegativity

Answer 15

Relative measure of the attraction that an atom has for a shared pair of electrons when it is covalently bonded to another atom

Question 16

Why does electronegativity increase across a period?

Answer 16

Due to increase in nuclear charge - increased attraction between nucleus and bond electrons

Question 17

Why does electronegativity decrease down a group?

Answer 17

Bonding electrons are further from the nucleus so reduced attraction

Question 18

Alkali metals (5)

Answer 18

Silvery metals, very reactive, good conductors, low densities, form ionic compounds with non-metals

Question 19

Halogens (3)

Answer 19

Coloured, very reactive, form ionic or covalent

Question 20

Displacement reactions

Answer 20

A more reactive element (higher in group) displaces a less reactive element (lower in group) from a compound that contains the less reactive element.

Question 21

Lewis Acid

Answer 21

Can accept an electron pair (non-metal oxides)

Question 22

Lewis base

Answer 22

Can donate an electron pair (many metal oxides)

Question 23

Lewis bases + metal oxides

Answer 23

React with water to form hydroxides.

Question 24

Amphoteric

Answer 24

Can act as an acid or base

Question 25

Acid rain

Answer 25

Solutions with a lower pH than 5.6 due to presence of sulfur and nitrogen oxides

Question 26

Sulfur oxides in creating acid rain

Answer 26

Sulfur dioxide dissolves in rainwater to form sulfric or sulfurous

H2O + SO2 -> H2SO3

• It can also be oxidised to sulfur trioxide, forming sulfric acid

Question 27

Nitrogen oxides in creating acid rain

Answer 27

Nitrogen dioxide dissolves in rainwater to form nitric or nitrous acid

Question 28

Ocean acidification due to carbon dioxide

Answer 28

About 50% of CO2 produced by combustion of fossil fuels is dissolved in oceans. CO2 reacts with water to make carbonic acid.

CO2 (aq) + H2O (l) -> H2CO3 (aq)

Question 29

Displacement reactions examples

Answer 29

Cl2 + 2Br- -> Br2 + 2Cl- (colourless to orange)

Cl2 + 2I-/Br2 + 2I- (colourless to dark orange/brown)

Question 30

Base/acid across a period

Answer 30

Changes from basic to amphoteric to acidic

Question 31

Metal oxides are

Answer 31

Bases (react with water to form hydroxides). Group 2 oxides also do this.

Question 32

Non metal oxides

Answer 32

Acids (react with water to form more acid)