Electrons and Charge

A proton has a charge of +1, an electron −1, a neutron 0. In a neutral atom the electrons balance the protons.

$$\text{charge} = \text{protons} - \text{electrons}$$

Oxygen that gains 2 electrons has 8 protons and 10 electrons: charge −2, written O²⁻. Sodium that loses 1 electron has charge +1, written Na⁺.

Oxygen with 8 electrons is neutral; with 10 it is O²⁻

Electrons never change the element: O²⁻ still has 8 protons, so it is still oxygen.