Which of the following sets of quantum numbers represents the last electron added to the iron (Fe) atom?

Question

Which of the following sets of quantum numbers represents the last electron added to the iron (Fe) atom?

-n = 3, ℓ = 2, m_ℓ = +1

-n = 3, ℓ = 0, m_ℓ = +1

-n = 3, ℓ = 1, m_ℓ = +1

-n = 4, ℓ = 1, m_ℓ = +2

-n = 4, ℓ = 2, m_ℓ = -1

Answer 1

Looking at the periodic table, we find iron (Fe) to be a transition metal location in period 4, group 8. The electron configuration for Fe is [Ar]4s²3d⁶ so the quantum numbers describing the last electron added would be...

n = 3

l = 2

ml = either -2, -1, 0, +1, +1

So only choice that is given that agrees with this would be the FIRST option: n = 3, ℓ = 2, m_ℓ = +1