Multiple Choice
How many unpaired electrons are present in a ground-state phosphorus (P) atom?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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How many core electrons and valence electrons does an aluminum (Al) atom have?
A
2 core electrons and 11 valence electrons
B
8 core electrons and 5 valence electrons
C
10 core electrons and 3 valence electrons
D
12 core electrons and 1 valence electron
Verified step by step guidance1
Identify the atomic number of aluminum (Al), which is 13. This means an aluminum atom has 13 electrons in total.
Recall that core electrons are those in the inner shells, while valence electrons are in the outermost shell.
Write the electron configuration of aluminum: $1s^2 2s^2 2p^6 3s^2 3p^1$.
Count the electrons in the inner shells (1s, 2s, 2p) to find the number of core electrons: $2 + 2 + 6 = 10$ core electrons.
Count the electrons in the outermost shell (3s and 3p) to find the number of valence electrons: $2 + 1 = 3$ valence electrons.
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