Multiple Choice
How many electrons can the first energy level (n = 1) of an atom hold?
3
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
How many valence electrons does magnesium (Mg) have?
A
6
B
4
C
2
D
8
Verified step by step guidance1
Identify the element magnesium (Mg) on the periodic table. Magnesium has an atomic number of 12, which means it has 12 electrons in total.
Determine the electron configuration of magnesium. The electrons fill orbitals in the order: 1s, 2s, 2p, 3s, etc. For Mg, the configuration is $1s^2 2s^2 2p^6 3s^2$.
Recognize that valence electrons are the electrons in the outermost shell (highest principal quantum number). For magnesium, the outermost shell is the third shell (n=3).
Count the electrons in the outermost shell. In the configuration $3s^2$, there are 2 electrons in the outermost shell.
Conclude that magnesium has 2 valence electrons because only the electrons in the outermost shell contribute to valence.
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