Question

How can I learn the valencies of the first 20 elements?

Answer 1

Valency:-

• Valency is defined as the property of an element in which it has the combining capacity with another atom of an element.
• It is related to electrons present in their outer orbital.
• Valency can be determined by their respective groups in the periodic table.

Determination of valency of first 20 elements:-

• The first 20 elements in a periodic table are Hydrogen $(\mathrm{H}-1)$, Helium $(\mathrm{He}-2)$, Lithium $(\mathrm{Li}-3)$, Berelium $(\mathrm{Be}-4)$, Boron $(\mathrm{B}-5)$, Carbon $(\mathrm{C}-6)$, Nitrogen $(\mathrm{N}-7)$, Oxygen $(\mathrm{O}-8)$, Fluorine $(\mathrm{F}-9)$, Neon $(\mathrm{Ne}-10)$, Sodium $(\mathrm{Na}-11)$, Magnesium $(\mathrm{Mg}-12)$, Aluminium $(\mathrm{Al}-13)$, Silicon $(\mathrm{Si}-14)$, Phosphorus $(\mathrm{P}-15)$, Sulphur $(\mathrm{S}-16)$, Chlorine $(\mathrm{Cl}-17)$, Argon $(\mathrm{Ar}-18)$, Potassium $(\mathrm{K}-19)$ and Calcium $(\mathrm{Ca}-20)$.
• Here Helium, Neon, and Argon are noble gases which have stable octet configurations, their valency is Zero (0).
• The first group of atoms in the periodic table are Hydrogen, Lithium, Sodium, and Potassium, their valency is one.
• The second group of elements are Beryllium, Magnesium, and Calcium and their valency is 2.
• Groups 3 - 12 are d-block elements in which the first 20 elements are not present.
• The group 13 elements include Boron and Aluminum which has valency 3.
• The group 14 elements have valency 4 which are Carbon, Silicon.
• The group 15 elements are Nitrogen and Phosphorus which have a valency of 5.
• Oxygen and Phosphorus are group 16 elements with valency 6.
• Fluorine and Chlorine have valency 7 which belongs to group 17.

Therefore, the valency of the first 20 elements can be determined by the unit value of their respective group number.