Question

What is the valency of Ca in the compound CaO.

Answer 1

Hint: Calcium is an atomic number 20 chemical element with the symbol Ca. Calcium is a reactive alkaline earth metal that produces a black oxide-nitride layer when exposed to air. It shares the same physical and chemical characteristics as its heavier homologues strontium and barium. After iron and aluminium, it is the fifth most plentiful element in the Earth's crust and the third most abundant metal.

Complete answer:
Calcium oxide (CaO), often known as quicklime or burned lime, is a chemical substance that is frequently used. At room temperature, it is a white, caustic, alkaline, crystalline solid. The word "lime" refers to calcium-containing inorganic compounds that are mostly composed of carbonates, oxides, and hydroxides of calcium, silicon, magnesium, aluminium, and iron. Quicklime, on the other hand, refers to the single chemical molecule calcium oxide. Free lime is calcium oxide that has not been processed and has not reacted in construction materials such as cement.
In chemistry, an element's valence or valency is a measure of its ability to combine with other atoms to create chemical compounds or molecules. The amount of hydrogen atoms that an atom of a certain element may combine with determines its combining capability, or affinity. Carbon has a valence of 4 in methane; nitrogen has a valence of 3 in ammonia; oxygen has a valence of 2 in water; and chlorine has a valence of 1 in hydrogen chloride. Because chlorine has a valence of one, it may be used to replace hydrogen. In phosphorus pentachloride, phosphorus has a valence of 5.
Ca has a valency of 2 in the combination CaO. Calcium is electropositive in nature, and in order to complete its octet, calcium atoms lose two electrons to create calcium cations with a valency of 2, requiring the matching anion, i.e. the oxide anion, to have a valency of 2 to balance the positive charge on the calcium cation.

Note:
According to Frankland, an element's valence is a single number that corresponds to the greatest value measured. The number of unused valencies on atoms of what are now known as p-block elements is typically even, and Frankland proposed that the unused valencies saturated each other. For example, nitrogen has a maximum valence of 5, so two valencies are left unconnected when producing ammonia; sulphur has a maximum valence of 6, so four valencies are left unattached when forming hydrogen sulphide.