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How many valence electrons are in a neutral atom of phosphorus (P)?
A
8
B
3
C
15
D
5
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1
Identify the element in question, which is phosphorus (P).
Determine the atomic number of phosphorus, which tells you the total number of electrons in a neutral atom. Phosphorus has an atomic number of 15.
Recall that valence electrons are the electrons in the outermost shell (energy level) of an atom.
Write the electron configuration of phosphorus to see how electrons are distributed in its shells: \$1s^2 2s^2 2p^6 3s^2 3p^3$.
Count the electrons in the outermost shell (the third shell here), which includes the \$3s^2$ and \$3p^3$ electrons, giving a total of 5 valence electrons.