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Given below are two statements. One is labelled as Assertion A and the other is labelled as Reason R. Assertion A: Energy of 2s orbital of hydrogen atom is greater than that of 2s orbital of lithium. Reason R: Energies of the orbitals in the same subshell decrease with increase in the atomic number. In the light of the above statements, choose the correct answer from the options given below.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is NOT the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Correct answer: Both A and R are true and R is the correct explanation of A.

Solution

The assertion is correct because the energy of orbitals increases with the addition of protons in the nucleus, making the 2s orbital of hydrogen higher in energy than that of lithium. The reason is also true as it explains that with an increase in atomic number, the effective nuclear charge increases, leading to lower energy levels for the same subshell, thus supporting the assertion.

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