Multiple Choice
Which of the following best describes how to use the periodic table to determine the number of valence electrons for a main-group element?
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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 chlorine (Cl) atom?
A
3s^2 3p^5
B
4s^2 4p^5
C
2s^2 2p^5
D
3s^2 3p^6
Verified step by step guidance1
Identify the atomic number of chlorine (Cl), which is 17. This means a neutral chlorine atom has 17 electrons.
Recall that electrons fill atomic orbitals in order of increasing energy levels, following the Aufbau principle: 1s, 2s, 2p, 3s, 3p, and so on.
Write the full electron configuration for chlorine by filling orbitals until you reach 17 electrons: 1s^2 2s^2 2p^6 3s^2 3p^5.
Determine the valence electrons by identifying the electrons in the outermost shell (highest principal quantum number n). For chlorine, the outermost shell is n=3, which includes 3s and 3p orbitals.
Express the valence electron configuration as 3s^2 3p^5, representing the electrons available for bonding and chemical reactions.
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