Multiple Choice
How many valence electrons does an oxygen atom have in its ground state?
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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 a neutral beryllium (Be) atom have?
A
8
B
4
C
2
D
6
Verified step by step guidance1
Identify the atomic number of beryllium (Be), which tells you the number of protons and, for a neutral atom, also the number of electrons.
Recall that beryllium has an atomic number of 4, so it has 4 electrons in total.
Determine the electron configuration of beryllium to find how these electrons are distributed among energy levels and orbitals. The configuration is $1s^2 2s^2$.
Recognize that valence electrons are the electrons in the outermost shell (highest principal quantum number). For beryllium, the outermost shell is the second shell (n=2).
Count the electrons in the outermost shell, which are the 2 electrons in the $2s$ orbital, so beryllium has 2 valence electrons.
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