(b) group 7 (halogens) - chlorine, bromine and iodine

colour, physical state and trends in physical properties of chlorine (2.5)

colour: green

state at room temperature: gas

colour, physical state and trends in physical properties of bromine (2.5)

colour: red-brown

state at room temperature: liquid

colour, physical state and trends in physical properties of iodine (2.5)

colour: grey

state at room temperature: solid

predict properties of other halogens using trends (2.6)

fluorine

colour: yellow

state at room temperature: gas

astatine

colour: black

state at room temperature: solid

trend for reactivity in group 7 (2.7 / 2.8C)

reactivity increases as you go up group 7 (i.e. fluorine is the most reactive whereas astatine is the least reactive)

a more reactive halogen will displace a less reactive halogen e.g. chlorine would displace bromine

this is because in fluorine, the outer electron shell is very close to the positively charged nucleus, so the attraction between the nucleus and the electrons is very strong, meaning that fluorine is incredibly reactive.