Answer:
This is due the different charges of fluoride and oxide ions.
Explanation:
When calcium reacts it is oxidized to Ca²⁺. In the same way, fluoride ion is reduced to F⁻ and oxide ion to O²⁻.
When these ions are combined, the molecule must be neutral. That means 2 ions of F⁻ are necessaries and just 1 O²⁻ ion will reacts producing:
CaF₂ and CaO.
The different charges of these ions is the reason why calcium will combine in different ratios.
Bonds formed between atoms can be classified as ionic and covalent
Ionic bonds are formed between atoms that have a high difference in the electronegativity values.
In contrast, bonds formed between atoms that have a difference in electronegativity lower than the ionic counterparts are polar covalent bonds. If the atoms have very similar electronegativities, they form non-polar covalent bonds.
In H2S, the S atom is bonded to 2 H atoms. The electronegativity of H = 2.2 and S= 2.56. Since the difference is not high the bond formed will be covalent (polar covalent).
Some examples of metallic bonds in copper, aluminum/Gold and even silver
