Question

when an atom loses an electron it becomes charged

Answer 1

When an atom loses an electron, the total positive charge upon it becomes more than the negative charge (since it loses an e- ; e- carries negative charge). So, it is said that it acquires positive charge.

Answer 2

When an atom loses an electron due to the ionic bond or any other reason as the number of the electron decreases the number of protons in the atom are more when compared to that of the electrons. So, when an atom loses an electron it becomes positively charged because protons number is more in the atom.