Multiple Choice
Which element has 3 energy levels and 4 valence electrons?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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Which of the following best describes the core electrons in a phosphorus (P) atom?
A
The 1s, 2s, and 2p electrons
B
Only the 1s electrons
C
The 3s and 3p electrons
D
All electrons except the 1s electrons
Verified step by step guidance1
Recall that core electrons are the electrons in an atom that are not involved in chemical bonding and are located in the inner shells, closer to the nucleus.
Identify the electron configuration of phosphorus (P), which has an atomic number of 15. The configuration is: $1s^2 2s^2 2p^6 3s^2 3p^3$.
Determine which electrons are valence electrons. For phosphorus, the valence electrons are those in the outermost shell, which is the third shell: $3s^2 3p^3$.
Recognize that core electrons are all electrons except the valence electrons. Therefore, the core electrons are those in the $1s$, $2s$, and $2p$ orbitals.
Conclude that the best description of the core electrons in phosphorus is the electrons in the $1s$, $2s$, and $2p$ orbitals.
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