Atomic StructurehardNUMERICAL

A neutral atom of an element has the ground-state electronic configuration . Calculate the total numAtomic Structure Chemistry Question

Question

A neutral atom of an element $X$ has the ground-state electronic configuration $1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^5$. Calculate the total number of electrons in this atom that possess a magnetic quantum number $m = 0$.

Answer: 12

💡 Solution & Explanation

The atom is Chromium ($Z=24$). The subshells with their electrons are: $1s^2$ ($l=0, m=0 \rightarrow 2e^-$), $2s^2$ ($l=0, m=0 \rightarrow 2e^-$), $2p^6$ ($l=1, m=-1,0,1 \rightarrow 2e^-$ in $m=0$), $3s^2$ ($l=0, m=0 \rightarrow 2e^-$), $3p^6$ ($l=1, m=-1,0,1 \rightarrow 2e^-$ in $m=0$), $4s^1$ ($l=0, m=0 \rightarrow 1e^-$), $3d^5$ ($l=2, m=-2,-1,0,1,2 \rightarrow 1e^-$ in $m=0$ as they are singly occupied). Total = $2+2+2+2+2+1+1 = 12$.

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