Question

Assertion : In hydrogen and hydrogen like species, orbital energy depends only on the quantum number $n$ whereas in multi-electron atoms it depends on quantum numbers $n$ and $I$.
Reason: The principal quantum number determines the size and the energy of the orbital.

• A. If both assertion and reason are true and reason is the correct explanation of assertion.
• B. If both assertion and reason are true but reason is not the correct explanation of assertion.
• C. If assertion is true but reason is false.
• D. If both assertion and reason are false.

Answer 1

Answer: (B)

Hydrogen and hydrogen-like species contains on electron only. Thus the electrostatic interaction is in between the positively charged nucleus $(+Z e)$ and negatively charged electron (-e). Thus energy depends only on the value of principal quantum number n. $n$ also determines the size of the orbital. Whereas in case of multi-electron atoms, along with attraction between nucleus and electron they also posses electron-electron repulsion within an orbital. And thus the energy depends on both $n$ and l values where $l =$ azimuthal quantum number.