Multiple Choice
Which of the following represents the correct electron configuration for a neutral atom of scandium (atomic number 21)?
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10. Periodic Properties of the Elements
The Electron Configuration
Multiple Choice
Which of the following represents the noble gas electron configuration for an oxygen atom?
A
[He] 2s^2 2p^6
B
[Ne] 2s^2 2p^4
C
[Ne] 3s^2 3p^4
D
[He] 2s^2 2p^4
Verified step by step guidance1
Identify the atomic number of oxygen, which is 8. This means an oxygen atom has 8 electrons.
Recall that noble gas electron configurations use the electron configuration of the previous noble gas as a shorthand to represent core electrons.
Determine the noble gas that comes before oxygen in the periodic table. Since oxygen has 8 electrons, the noble gas before it is helium (He), which has 2 electrons.
Write the electron configuration for oxygen starting from helium: helium accounts for the first 2 electrons, then add the remaining 6 electrons in the 2s and 2p orbitals, resulting in 2s^2 2p^4.
Compare the given options to this configuration. The correct noble gas shorthand for oxygen is [He] 2s^2 2p^4.
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