Question:easy

The number of s, p, and d-electrons present in gallium is respectively:

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Identify the complete electronic configuration first; then sum electrons in each type of orbital (s, p, d) to answer.
Updated On: Jul 18, 2026
  • 8, 10, 13
  • 8, 15, 8
  • 6, 15, 10
  • 8, 13, 10
Show Solution

The Correct Option is D

Solution and Explanation

Step 1: Build the configuration in the order orbitals actually fill, not shell by shell.
Gallium has atomic number 31, and electrons fill orbitals in the order fixed by the $(n+l)$ rule:
\[ 1s, \; 2s, \; 2p, \; 3s, \; 3p, \; 4s, \; 3d, \; 4p \]
Following this filling order for 31 electrons gives:
\[ 1s^2\,2s^2\,2p^6\,3s^2\,3p^6\,4s^2\,3d^{10}\,4p^1 \]
Notice that $4s$ fills before $3d$, even though $3d$ belongs to a lower shell number.

Step 2: Now regroup the same electrons by subshell type for counting, ignoring the shell number.
s-type orbitals used: $1s, 2s, 3s, 4s$, each holding 2 electrons. p-type orbitals used: $2p, 3p, 4p$, holding 6, 6, and 1 electrons. d-type orbitals used: $3d$, holding 10 electrons.

Step 3: Add up the s-electrons.
\[ 2+2+2+2 = 8 \]

Step 4: Add up the p-electrons.
\[ 6+6+1 = 13 \]

Step 5: Add up the d-electrons.
\[ 10 \]

Step 6: Check the totals add back to 31.
\[ 8+13+10 = 31 \]
This matches gallium's atomic number, confirming the count.

Final Answer:
\[ \boxed{8, \; 13, \; 10} \]
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