Multiple Choice
How many valence electrons does magnesium (Mg) have in its ground-state electron configuration?
45
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9. Electrons in Atoms and the Periodic Table
Valence Electrons of Elements (Simplified)
Multiple Choice
In a neutral silicon atom (Si), how many valence electrons are in its outermost energy level?
A
8
B
6
C
2
D
4
Verified step by step guidance1
Identify the atomic number of silicon (Si), which is 14. This tells us the total number of electrons in a neutral silicon atom.
Determine the electron configuration of silicon by filling the energy levels in order: 1s, 2s, 2p, 3s, and 3p.
Write the electron configuration: \(1s^2\ 2s^2\ 2p^6\ 3s^2\ 3p^2\).
Recognize that the outermost energy level (also called the valence shell) for silicon is the third energy level, which includes the 3s and 3p orbitals.
Count the electrons in the 3s and 3p orbitals: \$3s^2\( means 2 electrons, and \)3p^2$ means 2 electrons, so total valence electrons = 2 + 2 = 4.
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