Multiple Choice
How many valence electrons does silicon (Si) have?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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Which element has an outer shell electron configuration of 2s^2 2p^5?
A
Nitrogen (N)
B
Neon (Ne)
C
Oxygen (O)
D
Fluorine (F)
Verified step by step guidance1
Identify the electron configuration given: 2s^2 2p^5. This notation describes the electrons in the second energy level (shell), specifically in the s and p subshells.
Recall that the 2s subshell can hold up to 2 electrons and the 2p subshell can hold up to 6 electrons. Here, 2s^2 means the 2s subshell is full, and 2p^5 means there are 5 electrons in the 2p subshell.
Add the electrons in the second shell: 2 (from 2s^2) + 5 (from 2p^5) = 7 electrons in the second shell. Since the first shell (1s) is full with 2 electrons, the total number of electrons is 2 (first shell) + 7 (second shell) = 9 electrons.
Use the total number of electrons to identify the element. The atomic number corresponds to the number of electrons in a neutral atom. An element with 9 electrons is Fluorine (F).
Confirm that the other options do not match this configuration: Nitrogen (N) has 7 electrons total, Oxygen (O) has 8, and Neon (Ne) has 10. Therefore, the element with the configuration 2s^2 2p^5 is Fluorine (F).
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