Multiple Choice
How many valence electrons does a fluorine atom have?
3
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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How many unpaired electrons are present in a ground-state boron (B) atom?
A
2
B
0
C
3
D
1
Verified step by step guidance1
Identify the atomic number of boron (B), which is 5. This means a neutral boron atom has 5 electrons.
Write the electron configuration for boron in its ground state. The order of filling orbitals is 1s, 2s, then 2p. So, the configuration is $1s^2 2s^2 2p^1$.
Recall that the 1s and 2s orbitals are fully filled with paired electrons, so they do not contribute to unpaired electrons.
Focus on the 2p subshell, which has three orbitals (2p_x, 2p_y, 2p_z). Since there is only one electron in the 2p subshell, it will occupy one of these orbitals alone, resulting in one unpaired electron.
Conclude that the number of unpaired electrons in a ground-state boron atom is 1.
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