Question

Assertion :The $5^{th}$ period of periodic table contains 18 elements not 32. Reason: n = 5 , $\ell$ = 0, 1, 2, 3. The order in which the energy of available orbitals 4d, 5s and 5p increases is 5s < 4d < 5p and the total number of orbitals available are 9 and thus 18 electrons can be accommodated.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

The $5^{th}$ period of periodic table contains 18 elements not 32.

n = 5 , $\ell$ = 0, 1, 2, 3. The order in which the energy of available orbitals 4d, 5s and 5p increases is 5s < 4d < 5p and the total number of orbitals available are 9 and thus 18 electrons can be accommodated.

In other words, in the fifth period, f orbitals are not filled.

Thus, both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Hence, the correct option is $\text{A}$