Define valency by taking examples of silicon and oxygen.

Valency: Valency refers to an element’s ability to combine or bond with other elements by gaining, losing, or sharing electrons in order to achieve a stable electron configuration.

Silicon (Si):
– Valence Electrons: Silicon has 4 valence electrons in its outermost shell.
– Goal for Stability: To achieve stability, silicon aims to have 8 electrons in its outer shell, following the octet rule.
– Valency of Silicon: With 4 valence electrons, silicon tends to either gain 4 more electrons or share its 4 valence electrons with other atoms to reach the stable octet configuration.
– Example – Silicon Dioxide (SiO2): In silicon dioxide, each silicon atom shares its 4 valence electrons with 2 oxygen atoms. This sharing creates strong chemical bonds, fulfilling the need for both silicon and oxygen to complete their outer shells and achieve stability.

Oxygen (O):
– Valence Electrons: Oxygen has 6 valence electrons in its outermost shell.
– Goal for Stability: Oxygen needs 2 more electrons to reach the stable octet configuration.
– Valency of Oxygen: With 6 valence electrons, oxygen tends to gain 2 more electrons or share its electrons with other atoms to achieve stability.
– Example – Water (H2O): In water, each oxygen atom shares electrons with 2 hydrogen atoms. This sharing allows oxygen to complete its outer shell by receiving electrons from hydrogen, forming covalent bonds and achieving stability.

In summary, valency describes an element’s tendency to bond with other elements by gaining, losing, or sharing electrons to attain a stable electron configuration. Silicon with a valency of 4 forms compounds like silicon dioxide, while oxygen with a valency of 2 forms compounds like water, by sharing electrons to fulfill the octet rule and achieve stability.