Group 7 - Halogens

Question 1

What are the appearances for the group 7 halogens?

Answer 1

Flourine = very pale yellow gas ( highly reactive )
Chlorine = greenish, reactive gas ( poisonous in high concentrations )
Bromine = Red liquid ( gives off dense brown/ orange fumes )
Iodine = Shiny grey solid (sublimes to purple gas )

Question 2

What is the trend in melting and boiling point?

Answer 2

Increases down the group, as the molecules become larger they have more electrons and so the van der waals forces between molecules become larger. As the intermolecular forces get larger more energy has to be put in to break the forces. This increases the melting and boiling point.

Question 3

What is the trend for electronegativity?

Answer 3

As one goes down the group, the electronegativity of the element decreases.
As one goes down the group, the atomic radius increases due to the increasing number of shells. The nucleus is therefore less able to attract the bonding pair of electrons.

Question 4

What are the states of the halogens?

Answer 4

Fluorine = Gas
Chlorine = Gas
Bromine = Liquid
Iodine = Solid

Question 5

What happens in the displacement reactions by halogens?

Answer 5

A halogen that is a strong oxidising agent will displace a halogen that has a lower oxidising power from one of its compounds.

Question 6

Does the oxidising strength increase or decrease down the group?

Answer 6

The oxidising strength decreases down the group. Oxidising agents are electron acceptors.