Question

How are valence electrons used by an element?

Answer 1

Valence electrons are the ones present in the outermost shell of the atom. An element's valence electron can tell us about its ability to react and not react.

Complete answer:
In chemistry, the valence electrons are the electrons present in the outermost shell or the valence orbital of the atom. These are the most loosely bound electrons to the nucleus of the atom. The electrons in the valence shell are very important for any atom because these are the electrons which are directly participating in the process of chemical reaction.
For example, in any organic compound, the single bond between carbon and hydrogen will share one electron from the valence orbital of carbon and another from valence subshell of hydrogen.
The valence electron of any element decides almost all of its chemical properties like electronegativity, reactivity, ionisation energy etc. If in the valence shell of an atom we have only one atom, so it will try to get rid of that single electron to fulfil its octet.
If we add one electron in the valence shell of the atom, it will become a charged ion, called anion and if we remove one of the valence electrons from the valence shell of the atom, it will behave as a cation with electron deficiency.
Let us suppose a chemical reaction in which there is the formation of hydrochloric acid, then one electron from the valence shell of hydrogen atom will be shared to the valence shell of chlorine atom.

Note: For example, Na has one valence electron and Cl has seven valence electrons. They can form an ionic bond because they make up an octet atom, and hence results in the completion of the chemical reaction.