Metals on the left of the Periodic Table.
Non-Metals on the top-right, plus Hydrogen.
1:23 Understand why elements in the same group of the Periodic Table have similar chemical properties
Elements in the same group of the periodic table have the same number of electrons in their outer shells, which means they have similar chemical properties.
If you look at the trends in the physical properties of the halogens, Cl2, Br2, I2 you can make predictions about the properties of the other halogens.