Group 7 - Halogens

Fluorine, chlorine, bromine, iodine and astatine. 

7 electrons in outer shell so all react by gaining an electron to form a negative ion. 

Similar physical properties.

Further down group 7, less reactive because less inclination to gain extra electron to fill outer shell when further out from nucleus (larger atomic radius).

Melting and boiling points increase further down.

At…