Multiple Choice
What is the ground-state electron configuration of zinc (Zn) in noble-gas shorthand notation?
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9. Electrons in Atoms and the Periodic Table
The Electron Configuration (Simplified)
Multiple Choice
What is the ground-state electron configuration for cadmium (Cd), atomic number 48, in noble-gas shorthand notation?
A
[Kr]
B
[Ar]
C
[Kr]
D
[Kr]
Verified step by step guidance1
Identify the atomic number of cadmium (Cd), which is 48. This means cadmium has 48 electrons to arrange in its electron configuration.
Recall the noble gas that precedes cadmium in the periodic table. Krypton (Kr) has an atomic number of 36, so use [Kr] as the noble-gas shorthand to represent the first 36 electrons.
Determine the electron configuration for the remaining electrons after [Kr]. Since 48 - 36 = 12 electrons remain, these will fill the 4d and 5s orbitals.
Fill the 5s orbital first because it has lower energy than the 4d orbital, so place 2 electrons in 5s: \$5s^{2}$.
Next, fill the 4d orbital with the remaining 10 electrons: \$4d^{10}$. Combine this with the noble gas shorthand to write the full configuration as \([\mathrm{Kr}]\ 4d^{10}\ 5s^{2}\).
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