Does beryllium's gains or losses ion?

You question is a bit incorrect.

Beryllium is a metallic element in Group (II) of the Periodic Table.

Being in Group (II) it will have a strong tendency to loose electrons(ionisation).

In its neutral state beryllium has the electron structure of 1s2, 2s2, This means that its inner most electron shell (1s) contains two electrons.

Its outer most electron shell (2s) also contains two electrons.

When beryllium ionises two electrons , they are 'lost' from the outer most (2s) electron shell. They are further from the nucleus of the atom and are not so strongly held.!!!!!

When these two electrons have 'gone' , the Beryllium atom is now the Beryllium ION. (It is no longer an atom).

Formulaically it is written as

Be(g) = Be^(2+) + 2 e^(-)

So for beryllium atom to become a Beryllium ION it LOSES TWO electrons.