Group 7

Question 1

Physical properties of group 7 : atomic radii

Answer 1

Atomic radius increases down the group, more shielding less nuclear attraction between outer. electron and nucleus

Question 2

Physical properties of group 7:
Melting point.

Answer 2

Increases down the group, more van Der waal forces which increase as molecule increases.

Question 3

Electronegativity

What is it?

Answer 3

Decreases down the group, more shielding.

Electronegativity—–> power of an atom to attract the electron density of a covalent bond towards itself.

Question 4

Solubility of halides

Answer 4

Dissolve better in non polar liquids compared to water.

I= violet in hexane

Question 5

Oxidising ability of Halides

F2+2e——->2F-

Answer 5

Oxidising ability decreases down the group.

Atoms larger=harder to gain electron.

Reactions with metal halides.

Question 5

Reactivity of halides

Answer 5

Decreases down the group. More shelling and atomic radii, more difficult to gain electron.

Question 6

Reducing ability of Halides

2F—–>F2+2E-

Answer 6

Increases down the group
Iodine = greater distance easier to lose electron.
Cl= no redox white fumes acid base reaction.

Br= redox brown fumes misty white

I= redox black solid HS2 formed bad egg smell.

Question 7

Tests for Halides

Answer 7

Add HNO3 acid to remove ions
Add AgNO3

Cl= white
Br=cream
I=yellow

Add excess NH3
Cl= dissolves in dilute NH3
Br= dissolves in conc NH3
I=no dissolving

Question 8

Halide in bleach

Answer 8

2NaOH + Cl2 ——> NaClO+NaCl+H2O

Sodium chlorate

Disproportionation reaction chloride being both reduced and oxidised

Question 9

Halide to clean water

Answer 9

Cl2+H20 (reversible reaction) HClO + HCl

weak acid so dissociates
cleans water and kills bacteria