Why did it require two sodium atoms to complete the Na2O formula unit? Na has + 2 charge and O has - 1 charge. Na has + 1 charge and O has - 2 charge. Na has - 2 charge and O has + 1 charge.

Na₂O is an ionic compound. Na is in group 1 which means it has one electron in the outer shell. O is in group 6 so it has 6 electrons in the outer shell.

To become stable atoms need to either lose the electrons in the outer shell or gain electrons to gain a complete outer shell configuration.

To become stable Na loses its outer electron and becomes positively charged. It only loses one electron, so net charge is + 1. O to become stable gains 2 electrons to complete its outer shell and becomes negatively charged. since it gains 2 electrons, the net charge is - 2.

cation - Na⁺

anion - O²⁻

O gains 2 electrons but Na can give only one electron, therefore 2 Na⁺ ions are required.

the compound can be written by exchanging the charges

ions Na⁺ O²⁻

charge + 1 - 2

exchange Na₂O

Correct answer is Na has + 1 charge and O has - 2 charge