Multiple Choice
How many valence electrons are present in a neutral atom of fluorine?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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Which of the following represents the valence electron configuration for a selenium (Se) atom?
A
4s^2 3d^{10} 4p^4
B
4s^2 4p^6
C
4s^2 4p^4
D
3d^{10} 4s^2 4p^2
Verified step by step guidance1
Identify the atomic number of selenium (Se), which is 34. This tells us the total number of electrons in a neutral selenium atom.
Recall that valence electrons are the electrons in the outermost principal energy level (highest n value). For selenium, the outermost shell is the 4th shell (n=4).
Write the full electron configuration of selenium to understand the distribution of electrons: start filling from the lowest energy orbitals up to the 34th electron, following the Aufbau principle.
Focus on the electrons in the 4th shell (n=4), which includes the 4s and 4p orbitals. The 3d orbitals belong to the 3rd shell and are considered core electrons, not valence electrons.
Determine the valence electron configuration by including only the electrons in the 4s and 4p orbitals. For selenium, this corresponds to $4s^2 4p^4$.
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