Question 1 Page 52 (Left) - Chapter 4 Class 9 - Structure of Atom

How will you find the valency of chlorine, sulphur and magnesium?

Answer

(i) Chlorine

• Atomic number of chlorine = 17
• Electronic configuration of chlorine is - 2, 8, 7

• Number of valence electrons = 7

• Since atom has 7 valence electrons it is easier for the atom to gain 1 electron to achieve an octet.

Valency of atoms gaining 1 electron = 1

Therefore, Valency of chlorine = 1

(ii) Sulphur

• Atomic number of Sulphur = 16
• Electronic configuration of sulphur is - 2, 8, 6

• Number of valence electrons = 6

• Since the atom has 6 valence electrons it is easier for it to gain 2 electrons to achieve an octet .

Valency of atoms gaining 2 electrons = 2

Therefore, Valency of sulphur = 2

(iii) Magnesium

• Atomic number of magnesium = 12
• Electronic configuration of magnesium is - 2, 8, 2

• Number of valence electrons = 2

• Since the atom has 2 valence electrons it is easier for it to lose 2 electrons to achieve an octet .

Valency of atoms losing 2 electrons = 2

Therefore, Valency of magnesium = 2