Multiple Choice
Which of the following electron configurations correctly represents a neutral nitrogen atom?
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10. Periodic Properties of the Elements
The Electron Configuration
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How many unpaired electrons are present in a ground state atom of ruthenium (Ru)?
A
6
B
0
C
4
D
2
Verified step by step guidance1
Identify the atomic number of ruthenium (Ru), which is 44. This tells us that a neutral Ru atom has 44 electrons.
Write the electron configuration for Ru in its ground state. Start by filling the orbitals in order of increasing energy: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, and 4d.
Note that the electron configuration for Ru is [Kr] 5s^1 4d^7, where [Kr] represents the electron configuration of krypton (the noble gas preceding Ru).
Determine the distribution of electrons in the 4d subshell, which has 7 electrons. According to Hund's rule, electrons fill degenerate orbitals singly before pairing up, so place one electron in each of the five 4d orbitals, then pair the remaining two electrons.
Count the number of unpaired electrons in the 4d subshell after filling according to Hund's rule. This count gives the number of unpaired electrons in the ground state of Ru.
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