Group 7 - Halogens

• Group 7 is made up of fluorine, chlorine, bromine, iodine and astatine
• All Group 7 elements have 7 electrons in their outer shell so they all react by gaining one electron to form a negative ion.
• This means they all have similar properties.
• As you go down group 7 the melting points and boiling points of the halogens increase.
• This means at room temperature:                

• Chlorine (Cl2) is a fairly reactive, poisonous, dense green gas (low boiling point)
• Bromine (Br2) is a dense, poisonous, orange liquid
• Iodine (I2) is a dark grey crystalline solid (high boiling point)

• Halogens are keen to gain an electron to form 1- ion with a stable electronice structure.
• The more reactive the halogen the happier it is to gain an electron.
• Gain of electrons is called reduction

sodium + chlorine → sodium chloride