Question

A species having 8 electrons in the third shell is very reactive while the other species having 8 electrons in the third shell is very inactive they are :
1. K and Ar
2. K and Ca
3. Ca and Ar
4. Cl^- and Ar

Answer 1

Correct Answer - Option 1 : K and Ar

The correct answer is K and Ar.

Explanation:

• Potassium (K):
  • Potassium is a chemical element with the atomic number 19 and the symbol K.
  • Potassium has an extra shell of electrons, resulting in 8 more electrons in the third shell. 
  • This extra shell of electrons protects the outer electron from the nucleus's attractive force. 
  • As a result, less energy is required to remove potassium's outer electron, making it more reactive.

So, Potassium (K) having 8 electrons in the third shell is very reactive.

• Argon:
  • Argon is a noble or inert gas with the atomic number 18 and the symbol Ar.
  • Argon is inactive (non-reactive) because in the third shell 8 electrons are present.
  • When the elements react, their atoms complete their outer shells by losing, gaining, or sharing electrons. 
  • Noble gas (Argon) atoms have complete outer shells and do not lose, gain, or share electrons.

So, Argon (Ar) having 8 electrons in the third shell is very inactive.

Thus, K having 8 electrons in the third shell is very reactive while the Ar having 8 electrons in the third shell is very inactive.