Answer:
1:1
Step-by-step explanation:
The ratio of metal cationic atom to non-metal anionic atom in the compound is 1:1.
This is an ionic compound.
- This is because metal cationic atom has two valence electrons.
- Non-metal anionic oxygen has six valence electrons
- Calcium loses two of its valence electrons to be isoelectronic with Ar and this confers a stable configuration to it.
- Non-metal oxygen atom accepts the electrons and adds 2 to its 6 electrons to become isoelectronic with neon.
- So, 1 metal cationic atom combines with 1 non-metal anionic atom to form the compound.