Multiple Choice
Which element has 7 valence electrons in its 5th energy level?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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Which of the following represents the valence electron configuration for a potassium (K) atom?
A
3s^2 3p^6
B
4s^1
C
4p^1
D
3d^1
Verified step by step guidance1
Recall that the valence electrons are the electrons in the outermost shell (highest principal quantum number, n) of an atom.
Determine the atomic number of potassium (K), which is 19, meaning it has 19 electrons in total.
Write the electron configuration of potassium by filling orbitals in order of increasing energy: 1s^2 2s^2 2p^6 3s^2 3p^6, which accounts for 18 electrons.
The next electron after 3p^6 goes into the 4s orbital, so the valence electron configuration for potassium is 4s^1.
Understand that 3s^2 3p^6 represents the filled inner shell (n=3), 4p^1 and 3d^1 are not correct for potassium's ground state valence electrons.
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