Multiple Choice
In the simplified valence-electron model for main-group elements, how many valence electrons does a calcium (Ca) atom have?
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9. Electrons in Atoms and the Periodic Table
Valence Electrons of Elements (Simplified)
Multiple Choice
An atom of chlorine has several valence electrons in its ______.
A
second energy level only (n = 2)
B
nucleus
C
innermost electron shell (first energy level, n = 1)
D
outermost electron shell (third energy level, n = 3)
Verified step by step guidance1
Understand that valence electrons are the electrons located in the outermost electron shell (energy level) of an atom. These electrons are important because they participate in chemical bonding.
Recall the electron configuration of chlorine, which has an atomic number of 17. This means chlorine has 17 electrons arranged in energy levels around the nucleus.
Identify the energy levels (shells) where these electrons are placed: the first energy level (n = 1) can hold up to 2 electrons, the second energy level (n = 2) can hold up to 8 electrons, and the third energy level (n = 3) holds the remaining electrons.
Since chlorine has 17 electrons, after filling the first and second energy levels (2 + 8 = 10 electrons), the remaining 7 electrons occupy the third energy level, which is the outermost shell.
Therefore, the valence electrons of chlorine are located in the outermost electron shell, which is the third energy level (n = 3).
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