Multiple Choice
How many unpaired electrons are present in a sulfur (S) atom in its ground state?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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Which element has 5 valence electrons in the third energy level?
A
Sulfur (S)
B
Chlorine (Cl)
C
Phosphorus (P)
D
Nitrogen (N)
Verified step by step guidance1
Identify the third energy level as the principal quantum number n = 3, which corresponds to the third shell of electrons in an atom.
Recall that valence electrons are the electrons in the outermost shell (highest principal quantum number) of an atom.
Determine the electron configuration of each element to find how many valence electrons they have in the third energy level:
For example, phosphorus (P) has the electron configuration: $1s^2 2s^2 2p^6 3s^2 3p^3$, meaning it has 2 electrons in the 3s subshell and 3 electrons in the 3p subshell, totaling 5 valence electrons in the third energy level.
Compare this with sulfur (S), chlorine (Cl), and nitrogen (N) to confirm that phosphorus is the element with exactly 5 valence electrons in the third energy level.
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