Why do some elements need to form compounds with themselves?Watch
Metals lose their outer shell electrons forming a lattice of positive metal ions surrounded by a cloud of delocalised electrons
Group 4 elements form giant covalent structures (Like Diamond!) where each atom is covalently bonded to a number of other atoms to fill up their electron outer shell (e.g. 4 in carbon)
Groups 5,6 & 7 generally form relatively small molecules such as O2 by sharing electrons between the molecules to fill up their outer electron shell
Noble Gasses have a full outer shell so are just single atoms
Metals lose electrons as it is far easier for them to lose these 1-3 electrons than gain 7-5 electrons, similar idea for gaining the electrons for the other compounds
Hope this helped!
If an element bonds to itself, it can't be a compound - a molecule maybe, but not a compound.