Question

which of the following is the shorthand electron configuration of just fe (the atom, not the cation.) ar4s² ar4s²3d⁵ ar4s²3d⁶ ar4s²3d⁹

Explanation:

• Iron (Fe) has an atomic number of 26.
• The noble gas core for Fe is [Ar] (which has 18 electrons).
• We need to account for the remaining \(26 - 18=8\) electrons.
• The 4s orbital fills before the 3d orbital. The 4s orbital can hold 2 electrons.
• So, we have \(8 - 2 = 6\) electrons left for the 3d orbital.

Answer:

$$ [Ar]4s^{2}3d^{6} $$