In the periodic table:
You can imagine a zig-zag line, starting at B-Al-Si, separating metals from non-metals.
The outer shell of a metal is, therefore, less than half full of electrons. For this reason, metals are more likely to lose electrons to form a full outer shell.
Non-metals are mostly found in groups 5, 6 and 7. These non-metals will have 5, 6 or 7 electrons in the outer shell.
The outer shell of a non-metal is, therefore, more than half full of electrons. For this reason, non-metals are more likely to gain electrons to form a full outer shell.
The pattern of reactivity of the group 1 elements and the group 7 elements shows the general pattern for the reactivity of other groups.
|Groups||Type||Pattern of reactivity|
|1, 2, 3||Metal||Reactivity increases down the group|
|5, 6, 7||Non-metal||Reactivity decreases down the group|