The number of valence electrons in an atom is closely related to its valency. Valence electrons are the electrons in the outermost energy level or shell of an atom. They are involved in the atom's chemical reactions and bonding with other atoms.
The valency of an atom represents its ability to form chemical bonds with other atoms. It indicates the number of electrons an atom can gain, lose, or share in order to achieve a stable electron configuration, typically resembling that of a noble gas.
The valency of an atom is often determined by the number of valence electrons it possesses. In general, atoms tend to gain, lose, or share electrons to achieve a full outer electron shell, which is typically eight electrons, known as the octet rule. However, there are exceptions for atoms with fewer than or more than four valence electrons.
The relationship between the number of valence electrons and valency can be summarized as follows:
Atoms with 1-4 valence electrons tend to lose these electrons to achieve a stable configuration. The valency is equal to the number of electrons lost. For example, sodium (Na) has one valence electron and a valency of +1.
Atoms with 5-7 valence electrons tend to gain electrons to achieve a stable configuration. The valency is equal to eight minus the number of valence electrons. For example, chlorine (Cl) has seven valence electrons and a valency of -1.
Atoms with 8 valence electrons are already stable and have a valency of 0. These atoms are generally the noble gases, such as helium (He), neon (Ne), and argon (Ar). They do not readily gain, lose, or share electrons.
Some atoms can have multiple valencies depending on the specific compound or situation. For example, iron (Fe) can exhibit a valency of +2 or +3 in different compounds.
It's important to note that the concept of valency provides a simplified understanding of chemical bonding and is a useful tool in predicting the behavior of elements in chemical reactions. However, it does not account for the full complexity of bonding patterns and should be used as a guideline rather than an absolute rule.