객관식
How many valence electrons does the sulfide ion, S^{2-}, have?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
객관식
Lithium has an atomic number of 3. How many electrons are present in its outermost (valence) shell?
A
1
B
0
C
2
D
3
검증된 단계별 안내1
Identify the atomic number of lithium, which is 3. This means lithium has 3 protons and, in a neutral atom, 3 electrons.
Recall the electron configuration order: electrons fill the lowest energy levels first. The first shell (n=1) can hold up to 2 electrons, and the second shell (n=2) can hold up to 8 electrons.
Distribute the 3 electrons of lithium starting from the first shell: fill the first shell with 2 electrons.
Place the remaining electron(s) in the next shell, which is the second shell. Since 2 electrons are in the first shell, the remaining 1 electron goes to the second shell.
Conclude that the outermost shell (valence shell) of lithium contains 1 electron.
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