Read the Assertion and Reason below and choose the correct option. — Atomic Structure Chemistry Question

💡 Solution & Explanation

Statement I is correct; according to the Aufbau principle, the 4s orbital has a lower $(n+l)$ value ($4+0=4$) than the 3d orbital ($3+2=5$), so it is filled first. Statement II is incorrect; although the 4s orbital penetrates closer to the nucleus (which lowers its energy), its average distance from the nucleus is actually greater than that of the 3d orbital. Therefore, correct answer is C.