Multiple Choice
Which of the following is the correct electron configuration for the oxide ion, O^{2-}?
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10. Periodic Properties of the Elements
The Electron Configuration
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Which of the following represents the core electrons in the electron configuration of cobalt (Co, atomic number 27)?
A
1s^2 2s^2 2p^6 3s^2 3p^6 3d^6 4s^2
B
1s^2 2s^2 2p^6 3s^2 3p^6 3d^7
C
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2
D
1s^2 2s^2 2p^6 3s^2 3p^6
Verified step by step guidance1
Step 1: Understand the difference between core and valence electrons. Core electrons are those in the inner shells that do not participate in chemical bonding, while valence electrons are in the outermost shell and are involved in bonding.
Step 2: Write the full electron configuration of cobalt (Co), which has atomic number 27. The configuration is $1s^2 2s^2 2p^6 3s^2 3p^6 3d^7 4s^2$.
Step 3: Identify the valence electrons for cobalt. For transition metals like Co, the valence electrons include the outermost s and d electrons, which are $3d^7$ and $4s^2$.
Step 4: Determine the core electrons by excluding the valence electrons. The core electrons are all electrons in the shells below the valence shell, which are $1s^2 2s^2 2p^6 3s^2 3p^6$.
Step 5: Match the core electron configuration to the given options. The correct representation of core electrons is $1s^2 2s^2 2p^6 3s^2 3p^6$.
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