Dear student,

Metals tends to lose electrons and Non-Metals tend to gain electrons in order to gain a stable configuration.

To explain it further I am giving an example:

In case of metals, let say Sodium the configuration is 2,8,1. You can see there is 1 valence electron. In order to gain a stable configuration, it will lose it's 1 electron.

In case of Non-Metals, let say Oxygen the configuration is 2,6. You can see there is a deficiency of 2 electrons in the valence shell. Thus, in order to gain stable configuration it will gain 2 electrons.

I hope it helps.

Hi! The reason why  non metals gain electrons in order to achieve a full stable outer shell. Hence, non-metals end up gaining electrons because they have more valence electrons than metals, so make a stable octet, it is easier for them to gain electrons rather than lose them.

Similarly, metals lose electrons becuase it is easier for them to make a stable octet by losing electrons and making a stable octet, and achieve a stable outer shell.

Another reason why metals lose electrons is because metals have relatively low ionization energies as compared to non metals, so it becomes easier for a metal to lose electrons as compared to non metals. Conversely, non metals have high ionization energies, so it makes sense for non metals to gain electrons instead.

Hope this helped!