A Short Note on Valence Electrons Key Features

If the outer shell of the electron is not closed, it is known as a valence electron. In the case of a single covalent bond, both electrons contribute one valence electron to form a shared pair; in the case of an ionic bond, both electrons contribute one valence electron and the bond is known as a single ionic bond.

The presence of valence electrons can influence the chemical properties of an element, such as its valency — whether or not it can form chemical bonds with other elements, and if so, how readily and with how many other elements. In this way, the reactivity of a given element is highly dependent on the electronic configuration of the element. A valence electron can only exist in the outermost electron shell of a main-group element; however, a valence electron can also exist in the innermost electron shell of a transition metal, whereas a main-group element cannot.

Chemical inertness is generally associated with the presence of an atom with a closed shell of valence electrons (i.e., the configuration of a noble gas).

Chemical Reactions

The bonding behaviour of an atom is governed by the number of valence electrons present in the atom. As a result, elements whose atoms have the potential to contain the same number of valence electrons are clustered together in the periodic table of the elements.

In terms of metallic elements, the most reactive type is an alkali metal of group 1 (for example, sodium or potassium), which is due to the fact that such an atom has only one valence electron. This one valence electron is easily lost during the formation of an ionic bond, which provides the necessary ionisation energy, resulting in the formation of a positive ion (cation) with a closed shell (e.g., Na⁺ or K⁺) with a closed shell. A group 2 alkaline earth metal (for example, magnesium) is slightly less reactive than a group 1 alkaline earth metal because each atom must lose two valence electrons in order to form a positive ion with a closed shell (for example, Mg⁺).

Electrical Conductivity

A metal, a nonmetal, or a semiconductor are all classified based on the electrical conductivity of their valence electrons. Valence electrons are also responsible for the chemical bonding of an element (or metalloid).

When in the solid state, metallic elements have a high electrical conductivity, which is characteristic of most metals. Consequently, metals are found to the left of nonmetals in each row of the periodic table, and as such, they have a smaller number of possible valence electrons than do nonmetals. Nevertheless, because the ionisation energy of a metal atom is small, a metal atom’s valence electron is relatively free to leave one atom and associate with another atom nearby when the metal atom is in the solid state. Such a “free” electron can be moved under the influence of an electric field, and the motion of the electron results in the generation of an electric current, which is responsible for the electrical conductivity of a metal. Copper, Aluminium, Silver, and Gold are examples of conductors that are both efficient and beautiful.

When an insulator is used, a nonmetallic element has low electrical conductivity and acts as a conductor. A valence shell that is at least half full is characteristic of such an element, which can be found toward the right of the periodic table (the exception is boron). It has a high ionisation energy, which means that when an electric field is applied, an electron cannot easily leave an atom, and as a result, such an element can only conduct very small electric currents. For example, diamond (which is an allotrope of carbon) and sulphur are both solid elemental insulators.

Conclusion

Valence electrons are the electrons that are closest to the nucleus of an atom. In the case of a single covalent bond, both electrons contribute one valence electron to form a shared pair; in the case of an ionic bond, both electrons contribute one valence electron and the bond is known as a single ionic bond.

Chemical inertness is generally associated with the presence of an atom with a closed shell of valence electrons (i.e., the configuration of a noble gas).The bonding behaviour of an atom is governed by the number of valence electrons present in the atom. 

When in the solid state, metallic elements have a high electrical conductivity, which is characteristic of most metals. Consequently, metals are found to the left of nonmetals in each row of the periodic table, and as such, they have a smaller number of possible valence electrons than do nonmetals.When an insulator is used, a nonmetallic element has low electrical conductivity and acts as a conductor. A valence shell that is at least half full is characteristic of such an element, which can be found toward the right of the periodic table (the exception is boron).