Multiple Choice
How many valence electrons does aluminum (Al) have available for bonding?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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Which of the following is the correct number of valence electrons in a neutral cadmium (Cd) atom?
A
10
B
8
C
2
D
12
Verified step by step guidance1
Identify the electron configuration of a neutral cadmium (Cd) atom. Cadmium has an atomic number of 48, so it has 48 electrons.
Write the full electron configuration for Cd: $1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^6 4d^{10} 5s^2$.
Determine which electrons are valence electrons. Valence electrons are the electrons in the outermost shell (highest principal quantum number, n). For Cd, the outermost shell is the 5th shell, which contains the $5s^2$ electrons.
Note that the $4d^{10}$ electrons are in the 4th shell and are considered part of the inner d-subshell, not valence electrons for main group behavior.
Conclude that the number of valence electrons in a neutral Cd atom is the number of electrons in the 5s subshell, which is 2.
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