Question

What would be the subscripts for the formula unit Ca_O_?

Answer 1

When Ca is an ion, what is its charge?

Answer 2

if you don't know then try recalling some other compound of Ca..like CaCl2.if you know the charge of Cl (as an ion ) you can find Ca 's charge...This method will be really helpful sometimes.

Answer 3

hint:
usually, the oxydation state of Oxygen is \(-2\), whereas the oxydation sate of Calcium is \(+2\), now, we have to swap such oxydation states, like below:
\[\huge {\text{C}}{{\text{a}}_{ - 2}}{{\text{O}}_{ + 2}}\]
please neglect minus sign and plus sign:
\[\huge {\text{C}}{{\text{a}}_2}{{\text{O}}_2}\]
then please and simplify