객관식
In a neutral silicon atom (Si), how many valence electrons are in its outermost energy level?
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9. Electrons in Atoms and the Periodic Table
Valence Electrons of Elements (Simplified)
Multiple Choice
In a simplified valence-electron model for main-group elements, how many valence electrons does beryllium (Be) have?
A
8
B
2
C
4
D
1
검증된 단계별 안내1
Identify the element in question, which is beryllium (Be).
Recall that the valence electrons are the electrons in the outermost shell (energy level) of an atom.
Determine the electron configuration of beryllium: its atomic number is 4, so it has 4 electrons.
Write the electron configuration for beryllium: \$1s^2 2s^2$.
Count the electrons in the outermost shell (the second shell, \$2s^2$), which gives the number of valence electrons for beryllium.
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