Question

What is valency? Discuss the classification of elements based on the valency.

Answer 1

Valency: Valency is defined as the combining capacity of an element with another atom to form a chemical bond.

• If the valence electrons of an element are equal to 1,2, or 3 then valency equals the number of valence electrons.
• If the element has valence electrons 4,5,6, or 7, then valency is equal to the number of electrons to be added to complete the octet. (valency = 8 - valence electrons)
• Nobel gases has the octet configuration, which means they have 8 valence electrons. For noble gas valency is zero.

Monovalent: An atom, ion, or chemical group with a valency of one, which thus can form one covalent bond is called monovalent.

• For examples, $\mathrm{Hydrogen},\mathrm{Sodium}\left(\mathrm{Na}\right),\mathrm{Potassium}\left(\mathrm{K}\right),\mathrm{Chlorine}\left(\mathrm{Cl}\right)\mathrm{e}.\mathrm{t}.\mathrm{c}$

Divalent: An atom, ion, or chemical group with a valency of two, which thus can form two covalent bonds is called divalent.

• For example, $\mathrm{Magnesium}\left(\mathrm{Mg}\right),\mathrm{Calcium}\left(\mathrm{Ca}\right),\mathrm{Oxygen}\left(\mathrm{O}\right)\mathrm{e}.\mathrm{t}.\mathrm{c}.$

Trivalent: An atom, ion, or chemical group with a valency of two, which thus can form two covalent bonds is called trivalent.

• For examples, $\mathrm{Aluminium}\left(\mathrm{Al}\right),\mathrm{Nitrogen}\left(\mathrm{N}\right)\mathrm{e}.\mathrm{t}.\mathrm{c}.$