Which compound is held together by ionic bonds?

A. S02

B. H20

C. CaCl2

D. CH4

Answer is: C. CaCl2.

Name of this chemical compounds is calcium chloride.

Calcium chloride is a inorganic salt with ionic bonds between calcium and chlorine.

It is a colorless crystalline solid at room temperature, highly soluble in water.

Calcium form cation with positive charge 2 + and chlorine form anion with negative charge 1-.

Electron configuration of calcium atom: ₂₀Ca 1s² 2s² 2p⁶ 3s² 3p⁶ 4s².

Atomic number of calcium is 20, it means that it has 20 protons and 20 electrons, so atom of calcium is neutral.

When calcium lost two electrons, it will have 20 protons (positive charge) and 18 electrons (negative charge), which means it has two protons more and it has + 2 oxidation number.