2.4 The Halogens

Question 1

How are the melting and boiling points of Halogens?

Answer 1

They have low melting and boiling points which increase going down the group

Question 2

How halogens behave with electricity and heat?

Answer 2

They are poor conductor of heat and electricity

Question 3

How are halogens molecules made up of?

Answer 3

Halogen molecules are made up of pair of atoms called diatomic molecules; the atoms in each pair are joined to each other by a covalent bond.

Question 4

How do Halogens react?

Answer 4

• They all have 7 electrons in outermost shell. So they need to get 1 more electron to achieve the stable electronic structure of a noble gas.
• Their reactivity decreases going down the group

Question 5

How do halogens react with hydrogen?

Answer 5

F2 + H2 = 2HF eplosive even at -200 degrees and in the dark
Cl2 + H2 = 2HCl explosive in sunlight but slow in dark
Br2 + H2 = 2HBr react only at over 300 degrees and with a platinum cathalist
I2 + H2 = 2HI react only over 300 degrees and with a platinum cathalist (very slow and reversible)

Question 6

How do Halogens react with metals?

Answer 6

The halogen atoms gain 1 electron. They form ions with 1 - charge

Question 7

Talk about displacement reactions between halogens

Answer 7

A more reactive halogen will displace a less reactive halogen from solutions of its salt.
For example: Chlorine will displace bromide ions which form bromine molecules:
Cl2 (aq) + 2KBr (aq) = 2KCl (aq) + Br2 (aq) chlorine + potassium bromide = potassium cloride + bromine
Fluorine (the most reactive) will displace all others but it reacts so violently with water that you cannot carry out reactions in aqueous solutions