Periodic Table - Grp VII

Question 1

group VII

• they are called _____ (meaning…)
• atomic structure

Answer 1

• halogens (halo- salt, gens - generator)

- Halogens are made up of small discrete molecules. They exist as diatomic molecule.

Question 2

physical properties of group VII (3)
Fluorine to iodine
- molecular formula

Answer 2

F₂, Cl₂, Br₂, I₂

1. colour
2. physical state at rtp
3. mp/bp

Question 3

trends down grp VII (5)

Answer 3

1. mp increases down grp
2. colour darker
3. physical states (gas-> liquid-> solid)
4. reactivity decreases
5. density increases

Question 4

reason trend down grp VII (1)

Answer 4

1. mp:
   - simple covalent structure
   - relative molecular mass increase
   - strong intermolecular forces of attraction between the discrete molecules
   - more energy needed to overcome the intermolecular forces
   - hence, mp increases down grp
2. reactivity:
   reactivity decrease
   - atomic size increase, number of electron shells increase
   - distance between the valence electrons and nuclei increases
   - electrostatic forces of attraction between the valence electrons and nuclei is weaker
   - harder to gain electron to get noble gas configuration

Question 5

chemical properties of grp VII (3)

Answer 5

1. reactive non-metals
2. gain one electron, -ve ions, charge of -1
3. act as oxidising agent, oxidising effect decrease down grp

Question 6

grp VII reactions with hydrogen

Answer 6

1. to form gaseous covalent hydrides in the presence of light/heat. These hydrides dissolve inwater to form acids

Eg
H₂ (g) + Cl₂ (g) –> 2 HCl (g)

lesser electron sheel -> closer to nucleus > gain electron faster -> faster redox reaction

Question 7

grp VII reactions with water

Answer 7

1. to form acids

Cl₂ (g) + H₂O (l) -> HCl (aq) + HOCl (aq)

Question 8

halides definition

Answer 8

negativel charged anions, to have stable electronic configuration

halogen: Cl₂, Br₂
halide: Cl⁻, Br⁻

Question 9

insoluble halides (2)

• what type of halide
• colour

Answer 9

1. silver halides
AgCl white 
AgBr cream 
AgI pale yellow 
Eg AgNO₃ (aq) + KCl (aq) -> AgCl (s) + KNO₃ (aq)  observation: white ppt (precipitate)
- no redox, no change in OS 

diff type of reaction
- redox - neutralisation - this experiment

2. Lead (II) halide
   PbCl₂ white
   PbBr₂ white
   PbI₂ bright yellow

Question 10

grp VII displacement reactions

• general statement
• general observation

Answer 10

• A more reactive halogen will displace a less reactive halogen from its aq salt
• displacement has occurred when there is a colour change

Question 11

grp VII displacement reactions

paragraphs (2)

Answer 11

got displacement:
chemical equation
The (colour)(salt solution) turns (colour)

(Halogen) is more reactive than (halogen) so it has a higher tendency to gain electrons to form anions. Hence it displaces (halogen) from (salt solution)

No displacement:
No visible reaction

(halogen) is less reactive than (halogen) so it has a lower tendency to gain electrons to form anions. Hence it cannot displace (halogen) from (salt solution)

Question 12

reason for trend down grp VII – chemical properties (1)

Answer 12

1. reactivity decreases down grp VII
   - size increases as number of electron shells increase
   - dist between the nucleus and valence electrons increase
   - electronic forces of attraction between valence electrons and nucleus weaker
   - more difficult to gain electron
   - therefore reactivity decrease down grp