2c) Group 7 elements

Chlorine, bromine and iodine
called Halogens

Properties:

Group VII elements	Atomic Number	Colour	At room temperature	Boiling Point
Chlorine	17	green	gas	-34C
Bromine	35	red-brown	liquid	59C
Iodine	53	dark grey	solid	185C

Bonding in molecules:

Displacement reactions:

• more reactive halogens displace less reactive ones 
• a solution of its salt 
• Cl2 + 2KBr -----> 2KCl + Br2 (orange-brown)
• Cl2 + 2KCl -----> 2KCl + I2 (dark brown)
• Br2 + 2KBr -----> 2KBr + I2 (dark brown) 
• REDOX Reactions 

Summary: Chlorine is smaller than bromine has less outer shells of electrons sheilding the nucleus 

attracts electrons more readily 

More reactive as the atomic number decreases 

HCl gas vs HCl (aq) 

• gas: covalently bonded 
• no ions so can't conduct electricity 
• not acidic 

HCl dissolved in water:

• forms H+ (aq) and Cl- (aq) 
• ions conduct electricity 
• solution acidic