Multiple Choice
1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 is the electron configuration for which element?
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10. Periodic Properties of the Elements
The Electron Configuration
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Which element has an electron configuration of 2–5, and how many protons does its atom contain?
A
2
B
12
C
7
D
5
Verified step by step guidance1
Understand that the electron configuration given, 2–5, means the element has 2 electrons in the first shell and 5 electrons in the second shell.
Recall that the total number of electrons in a neutral atom equals the number of protons in the nucleus.
Add the electrons in all shells to find the total number of electrons: 2 + 5 = 7 electrons.
Identify the element with 7 protons (and thus 7 electrons) by referring to the periodic table; this element is nitrogen (N).
Conclude that the element with electron configuration 2–5 is nitrogen, and it contains 7 protons.
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