Question

Which of the following is the correct arrangement of elements in increasing order of their valency?

• A. Neon < Hydrogen < Magnesium
• B. Neon < Magnesium < Hydrogen
• C. Magnesium < Hydrogen < Neon
• D. Hydrogen < Neon < Magnesium

Answer 1

The correct option is A Neon < Hydrogen < Magnesium

Valency is the combining capacity of an element. It is determined by the number of valence electrons.
If number of valence electrons are four or less than four, then valency = number of valence electrons
If number of valence electrons are greater than four, then valency = 8 - number of valence electrons $$\begin{array}{cccc}\text{Element}& \text{Atomic number}& \text{Electronic configuration}& \text{Valency}\\ \text{Neon}& \text{10}& \text{2, 8}& \text{0}\\ \text{Hydrogen}& \text{1}& \text{1}& \text{1}\\ \text{Magnesium}& \text{12}& \text{2, 8, 2}& \text{2}\end{array}$$ Hence, the increasing order of valency is: Neon < Hydrogen < Magnesium