Why did it require two sodium atoms to complete the Na2O formula unit?

A) Na has +2 charge and O has -1 charge.

B) Na has +1 charge and O has -2 charge.

C) Na has -2 charge and O has +1 charge.

For the reaction shown, find the limiting reactant for each of the following initial amounts of reactants. 4al(s)+3o2(g)→2al2o3(s) a) 1 molal, 1 mol o2 b) 4 molal, 2.6 mol o2 c) 16 molal, 13 mol o2 d) 7.4 molal, 6.5 mol o2