Question

202. If the valence shell electronic configuration for an element is ns²np⁵, this element will belong to the group of -

• A. alkali metals
• B. inert metals
• C. noble gases
• D. halogens

Answer 1

The correct option is D

halogens

Explanation of correct option:

(D)

• Here, the valence electron enters in p-subshell, so it is called the p-block element.
• The general electronic configuration of the valence shell for an element is given ns²np⁵.
• The general electronic configuration of the valence shell for this element shows that it has 7 valence electrons.
• The group number of an element with valence electrons more than 2 is equal to valence electrons plus 10.
• So in this case, the group number is equal to 7+10 = 17.
• Group number 17 is popularly known as halogens.

Explanation of incorrect option:

(A) Alkali metals:

• The general electronic configuration of the valence shell of alkali metals is ns¹.
• The alkali metals have 1 valence electron.
• The group number of an element having up to 2 valence electrons is equal to the number of valence electrons.
• Thus, the group number of alkali metals is 1.

(B) Inert Metals

• They are also known as noble metal
• They are chemically corrosion resistant and mostly found in raw form in the nature
• They are oxidation and corrosion resistant even at high temperatures

(C) Noble gases:

• The general electronic configuration of the valence shell of noble gases is ns²np⁶.
• The noble gases have 8 valence electrons.
• The group number of an element with valence electrons more than 2 is equal to valence electrons plus 10.
• So, the group number of noble gases is 8+10 = 18.

Conclusion: Hence, option(D) is correct.