(a) For the compound XF₂, X must be a metal. As fluorine is monovalent and there are two fluorine atoms, so the valency of X must be two.
Therefore, X belongs to group 2.
A metallic compound is a compound that contains one or more metal elements bonded to another element.
The elements are bonded with the help of metallic bonds.
Monovalent compounds are compounds which consist of an atom which has only a single covalent bond.
The covalent bond is defined as an interatomic linkage formed by sharing the electronic pair between two atoms.
Valency is the combining power of an element. It helps with bond formation.
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