difference between valence electrons and valency

Difference Between Valence Electrons and Valency

Valence electrons and valency are two terms that are frequently used in chemistry, but they can be confusing for some people. Both of these terms are related to the electronic configuration of an atom, but they have different meanings. In this article, we will explore the differences between valence electrons and valency.

What are Valence Electrons?

Valence electrons are the electrons that are present in the outermost shell of an atom. These electrons are involved in chemical reactions and bonding with other atoms. The number of valence electrons in an atom determines its chemical properties, such as its reactivity and its ability to form chemical bonds.

For example, the element sodium (Na) has one valence electron in its outermost shell. This makes sodium highly reactive and easily gives up its valence electron to form an ionic bond with another atom.

What is Valency?

Valency is the number of electrons that an atom needs to gain or lose to achieve a stable configuration. This stable configuration is usually the electron configuration of a noble gas. For example, the noble gas neon (Ne) has a stable electron configuration of 2,8. This means that valency of neon is zero, as it does not need to gain or lose any electrons to achieve a stable configuration.

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On the other hand, the element chlorine (Cl) has a valency of -1 as it needs to gain one electron to achieve a stable electron configuration of the noble gas argon (Ar). The element magnesium (Mg) has a valency of +2 as it needs to lose two electrons to achieve the stable electron configuration of the noble gas neon (Ne).

The Relationship Between Valence Electrons and Valency

Valence electrons and valency are related but they are not the same thing. The number of valence electrons determines the chemical behavior of an atom while the valency determines the number of electrons that an atom needs to gain or lose to achieve a stable configuration.

In general, the valency of an atom is equal to the number of valence electrons minus either eight (for elements in group 1, 2, and 3) or the number of valence electrons (for elements in groups 4, 5, 6, and 7). For example, the element sulfur (S) has six valence electrons and a valency of -2 as it needs to gain two electrons to achieve a stable electron configuration.

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In conclusion, understanding the difference between valence electrons and valency is crucial in understanding the chemical properties and behavior of atoms. While they are related, they have different meanings and play different roles in chemical reactions and bonding.

Table difference between valence electrons and valency

Valence Electrons Valency
Electrons present in the outermost shell of an atom The ability of an element to combine with other elements
Determines the chemical behavior of an element Determined by the number of valence electrons an element has
Valence electrons participate in chemical bonding Valency can be positive, negative, or neutral
Valence electrons can be represented using Lewis dot diagrams Valency is used to predict the formula and properties of compounds