The electronic configuration for Neodymium is:
[Atomic Number for Neodymium 60]

Solution

Chemistry ma’am · 3 steps

Take away xenon's 54 and only 6 electrons are left: two go to 6s, the other four go into 4f.

1. Electrons after xenon. Xenon has 54 electrons, so neodymium has 60 - 54 = 6 electrons beyond the [Xe] core.
2. Fill in order. After xenon the order is 6s, then 4f. So 6s takes 2 electrons first, and the remaining 4 enter 4f. Neodymium is a lanthanide, so the 4f subshell is the one being filled. It is not 5d, and it is not 5f.

   Option	Electrons counted	Problem
   (a) [Xe] 4f⁴ 6s²	54 + 4 + 2 = 60	none: matches Nd
   (b) [Xe] 5f⁴ 7s²	54 + 4 + 2 = 60	5f and 7s belong to period 7 (actinides)
   (c) [Xe] 4f⁶ 6s²	54 + 6 + 2 = 62	two electrons too many (this is Sm)
   (d) [Xe] 4f¹ 5d¹ 6s²	54 + 1 + 1 + 2 = 58	two electrons too few (this is Ce)

3. So. The configuration of neodymium is [Xe] 4f⁴ 6s², which is option (a).

The idea to keep. For a lanthanide, subtract 54 for the xenon core and put 2 electrons in 6s. The rest usually go into 4f. Always add the electrons back up to check that you reach the atomic number.

Answer from the NTA final answer key. Solution by PrepWiser.