Assertion : Atomic radius of gallium is higher than that of aluminium
Reason : The presence of additional d-electron offer poor screening effect for the outer electrons from increased nuclear charge.

Options

A. Assertion is correct, reason is correct, reason is a correct explanation for assertion.
B. Assertion is correct, reason is correct, reason is not a correct explanation for assertion
C. Assertion is correct, reason is incorrect
D. Assertion is incorrect, reason is correct.

Answer

A

Explanation

Both assertion and reason are true and reason is the correct explanation of assertion.
Radius `r_(n) = (n^(2)h^(2))/(4pie^(2) mZ) = (n^(2))/(Z) xx 0.529Å r_(n)`
For first orbit of H-atom
`n = 1`
`r_(1) =((1)^(2))/(1) xx 0.529Å = 0.529Å`