Question

1. which electron - dot formula represents calcium oxide?

o $:\ddot{\mathrm{ca}}:^{+} \mathrm{o}^{+}$
o $: \mathrm{ca}: \ddot{\mathrm{o}}:$
o $\mathrm{ca}^{2+}: \ddot{\mathrm{o}}:^{2-}$
o $\mathrm{ca}:: \ddot{\mathrm{o}}:$

Explanation:

Calcium oxide (\(CaO\)) is an ionic compound. Calcium (\(Ca\)) loses two electrons to form \(Ca^{2 + }\) ion, and oxygen (\(O\)) gains two electrons to form \(O^{2 - }\) ion. In the electron - dot formula for ionic compounds, the cation is written first (without dots around it if it has lost all its valence electrons), and the anion is enclosed in brackets with its charge shown outside the brackets.

Answer:

\(Ca^{2+}[\colon\ddot{O}\colon]^{2 - }\) (the third option)