Multiple Choice
Which of the following elements has eight valence electrons?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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For the sodium cation (Na^+), how many electrons are present in its valence shell, and how many unpaired electron spins does it have?
A
1 valence electron; 1 unpaired electron spin
B
2 valence electrons; 2 unpaired electron spins
C
0 valence electrons; 0 unpaired electron spins
D
8 valence electrons; 0 unpaired electron spins
Verified step by step guidance1
Identify the atomic number of sodium (Na), which is 11. This means a neutral sodium atom has 11 electrons.
Determine the electron configuration of neutral sodium: $1s^2\ 2s^2\ 2p^6\ 3s^1$.
Since the problem asks about the sodium cation $\text{Na}^+$, recognize that it has lost one electron compared to the neutral atom, so it has 10 electrons.
Write the electron configuration for $\text{Na}^+$ by removing one electron from the outermost shell: $1s^2\ 2s^2\ 2p^6$.
From this configuration, note that the valence shell is now the second shell ($n=2$) with $2s^2\ 2p^6$, which is fully filled, so there are 8 valence electrons and no unpaired electron spins.
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