Valency vs. Covalency

Main Difference

The main difference between valency and covalency is that valency is the number of electrons present in the outermost shell of an atom, whereas covalency is the number of electron pairs that an atom can share.

Difference Between Valency and Covalency

Comparison Chart

Valency vs. Covalency

Valency is considered as the number of electrons that an atom gains or loses to become stable, while covalency is the highest amount of covalent bonds that an atom can produce by using its free orbitals. Valency may be equal to the number of electrons present in the valence shell or vice versa, whereas covalency is only determined by the number of electrons present in the valence shell.

Valency usually provides the required number of electrons to complete all the free orbitals; on the other hand, covalency is determined by the number of free electrons that exist in an atom. Valency is set for elements that can either create a covalent bond or an ionic bond; on the contrary, covalency can be present only for elements that can create a covalent bond between them.

Valency could either have a positive value or a negative value; conversely, covalency is generally always a positive value. Valency of Sulphur in SF₆ is 2; on the flip side, the covalency of Sulphur in SF₆ is 6.

What is Valency?

The term valency means the number of electrons which an atom could either lose or gain to complete its octet shell. The electrons that are present in the outmost shell of an atom are the valence electrons. So, the number of electrons present in the valence shell of an atom is considered as the valency of a particular atom. For instance, consider hydrogen atom H, whose valency is one which could lose or can share more electrons from another atom to become stable.

Chlorine valency is one, and it has 7 electrons present in its outermost shell but chlorine gain one more electron from the other element to gain the properties of noble gas and become more stable because it is easy for chlorine atom to gain an electron from the other element rather lose its electrons. The valency of a specific atom or element could also be observed by the electronic configuration method.

Valency could either have a positive value or a negative value, which means positive sign on an atom indicates that the atom will gain electrons to become stable while the negative sign on atom indicates that the atom will remove its electrons to become stable. The periodic table in chemistry also indicates the valency of an atom. Examples of the valency of Sulphur in SF₆ are 2; in H₁ the valency is 1, etc.

What is Covalency?

The term covalency is defined in such a way that it is the highest amount of covalent bonds that an atom can produce by using its free orbitals. The number of valence electrons present in the outermost shell of an atom is the reason for the dependency of covalency. For instance, the number of electrons present in the valence shell of Hydrogen is one, and its covalency is also considered as one which is shared with other atoms to form a covalent bond.

Covalency is generally always a positive value. Because of the limited covalency capabilities of atoms is the main reason for the saturation of covalent bonds. Consequently, the covalency of an element is described by the total numbers of electrons present in the valence shell contributing to the development of covalent bonds.

Not only the number of electrons present in the valence shell but also the number of free orbitals of an atom are imperative in determining the covalency. Types of Covalency are constant covalency and variable covalency. Examples of the covalency of Sulphur in SF₆ is 6.

Conclusion

The above discussion concludes that the valency is the number of electrons present in the outermost shell of an atom and gain or lose its electrons to become stable, whereas covalency is the number of the combined electron that an atom can share to form a covalent bond.