Question

why mg atom gets positive 2 charge when it loses two electrons

Answer 1

when mg atom loses two electrons, its balanced state of having an equal number of protons and electrons is disrupted.
Since there are two electrons less, the number of protons happens to be greater than the number of electrons, thus making it positively charged.

HOPE THAT ANSWERS YOUR QUESTION
(PS. plz mark as brainliest)

Answer 2

As we know magnesium has atomic no. 12.

thereofore electronic configuration will be 2,8,2 ,i.e, 2 valence electrons.

therfore it can lose upto 2 electons and therefore can have +2 charge over it.

NOW THE REASON BEHIND THIS +2 CHARGE IS AS IT LOSES 2 ELECTRONS THEREFORE IT HAS 10 VALENCE ELCTRONS NOW.

IT MEANS NOW 2 EXTRA PROTONS ARE  THERE IN Mg+2 .

THEREFORE IT HAS +2 CHARGE WHEN IT LOSES 2 e's.