Question

an oxide ion, o$^{2-}$, has:
8 protons and 10 electrons
10 protons and 8 electrons
8 protons and 9 electrons
8 protons and 7 electrons
10 protons and 7 electrons

Explanation:

Step1: Determine proton number

Oxygen has an atomic number of 8, so the number of protons in an oxide ion ($O^{2 - }$) is equal to the atomic number of oxygen, which is 8.

Step2: Determine electron number

A neutral oxygen atom has 8 electrons. The oxide ion has a charge of $2 - $, meaning it has gained 2 electrons. So the number of electrons is $8 + 2 = 10$.

Answer:

8 protons and 10 electrons (the first option: 8 protons and 10 electrons)