Use the crossover method to find the chemical formula of a calcium oxide

CaO

how:

since its an iconic compound (metal(Ca)+non-metal(O)=iconic(CaO) we have to take account the charges

so;

now we will cross them

since both the values are same will cross it out.

hence: CaO

the answer is a and have a great day

every chemical equation adheres to the law of conservation of mass, which states that matter cannot be created or destroyed. therefore, there must be the same number of atoms of each element on each side of a chemical equation.