Someone help please i cant figure this out

2 : 1

Explanation:

Cation :

Ca - calcium = atomic number = 20

Electron dot configuration : 2, 8, 8, 2

Ca losses 2 electrons in its outermost shell and thus has a charge of 2+ in other to attain a stable octet state.

Anion:

F - has 7 valence electrons and thus needs 1 electron to achieve a stable octet state, hence it accepts one electron has has a charge of (-1)

Therefore,

Ratio of cation (+) to negative (-) = 2 :1

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