NEETChemistryStructure of Atom
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): In a multi-electron atom, an electron will occupy the 3d orbital before the 4p orbital. Reason (R): The (n+l) value for the 3d orbital is lower than the (n+l) value for the 4p orbital. In the light of the above statements, choose the most appropriate answer from the options given below:
Options
- ABoth (A) and (R) are true and (R) is the correct explanation of (A)
- BBoth (A) and (R) are true but (R) is not the correct explanation of (A)
- C(A) is false but (R) is true
- D(A) is true but (R) is false
Correct answer
D. (A) is true but (R) is false
Step-by-step solution
Assertion (A) is true: According to the Aufbau principle, electrons fill orbitals in order of increasing energy. The 3d orbital has lower energy than the 4p orbital, so it is occupied first. Reason (R) is false: The energy of an orbital is determined by the (n+l) rule. For the 3d orbital, n=3 and l=2 , giving (n+l) = 5 . For the 4p orbital, n=4 and l=1 , also giving (n+l) = 5 . The values are equal, not lower. When two orbitals have the same (n+l) value, the orbital with the lower value of n has lower energy and is