Question

Assertion (A): To have 2 or 8 electrons in the outermost shell of an atom is always considered to be the most stable arrangement of atoms.

Reason (R): Though 8 electrons in the outermost shell always impart stability to an atom, but 2 electrons in the outermost shell of an atom impart stability only when the outermost shell is the first shell (K shell), and no other shells are present in the atom.

Options

• Both A and R are true and R is correct explanation of the assertion.

• Both A and R are true but R is not the correct explanation of the assertion.

• A is true but R is false.

• A is false but R is true.

Answer 1

A is false but R is true.

Explanation:

Assertion (A) is incorrect since having 2 outer electrons is not always stable (for example, Magnesium has 2 outer electrons but is highly reactive), while Reason (R) correctly explains that 2 outer electrons only provide stability when limited to the first shell (K shell), whereas 8 outer electrons always ensure stability.