Which statement is correct about electron orbitals and energy levels?

A. Yttrium, $\ce{Y}$ ($Z = 39$) is the first element in the periodic table with an electron in a f sub-level.

B. The maximum number of electrons in one d orbital is 10.

C. The maximum number of electrons in the 4th main energy level is 18.

D. In a main energy level, the sub-level with the highest energy is labelled f.

I thought B and D are all possible solutions to this answer.

B--the maximum number of electrons in 1 d orbital is 10.

D--in main energy level, the sub-levels in order of increasing energy is s $<$ p $<$d $<$f

So why is the answer only D?

Please advise and sorry in advance for the wrong tags or title name, as I am new to the group and am trying to improve on it.

  • 6
    $\begingroup$ You mixed up a d orbital with the d subshell. One d subshell contains five d orbitals. $\endgroup$ Dec 31, 2015 at 4:23
  • 1
    $\begingroup$ @orthocresol, so for B, the maximum number of electrons in one d orbital should be 2? $\endgroup$
    – CCC
    Dec 31, 2015 at 4:26
  • 1
    $\begingroup$ Meowth, that's right! $\endgroup$ Dec 31, 2015 at 4:43
  • 4
    $\begingroup$ If you really want to blow your mind (and, incidentally, prove D as technically sort-of incorrect), look into g-orbitals, and h-orbitals, and i-orbitals, and .... $\endgroup$
    – hBy2Py
    Dec 31, 2015 at 4:47

1 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.


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