Question

Which of the following statements is correct concerning atomic orbitals and energy levels in the electron configurations of the known elements? The maximum number of electrons in a single d orbital is 10 Within main energy levels 4 and 5, the sub-level with the highest energy is labelled f Yttrium, Y, (Z = 39) is the first element in the Periodic Table with an electron in an f orbital The maximum number of electrons in the 4th main energy level is 18

Answer 1

Although @orthocresol got this first, and it should be credited to him, I'm posting it as an answer.

In option (B), the statement is incorrect as it refers to d orbitals, which can (according to Pauli's Exclusion Principle) hold 2 electrons each, rather than the d subshell, which can hold 10 electrons, as it has a total of 5 d orbitals which can hold 2 electrons each, and 5∗2=10.

Thus, only option (D) is correct.