Given below are two statements. One is labelled as Assertion A and the other is labelled as Reason R . Assertion A : Energy of 2 s orbital of hydrogen atom is greater than that of 2 s 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.

Step-by-step solution

As given in question (A) and (R) both are correct and (R) is the correct explanation of (A) We know that for the electron in the same orbital, attraction is more for a larger atomic number. An increase of attraction decreases the energy of the orbital and the electron present in it. Hence, the given reason in question is correct that energies of the orbitals in the same subshell decreases with an increase in the atomic number. Taking into account the given elements, 2 s - orbital (energy level) of H atom will have