Multiple Choice
Which of the following best describes valence electrons and their importance?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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Why is the calcium ion (Ca^{2+}) more stable than the calcium atom (Ca)?
A
Ca^{2+} has a full octet in its outermost shell, making it energetically more stable.
B
Ca^{2+} contains more protons than Ca, resulting in greater stability.
C
Ca^{2+} has a higher atomic number than Ca, which makes it more stable.
D
Ca^{2+} has more valence electrons than Ca, increasing its stability.
Verified step by step guidance1
Understand the electronic configuration of a neutral calcium atom (Ca). Calcium has an atomic number of 20, so its electron configuration is $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2$.
Recognize that the calcium ion $\text{Ca}^{2+}$ is formed by losing two electrons from the neutral atom. These electrons are removed from the outermost shell, which is the 4s orbital, resulting in the configuration $1s^2 2s^2 2p^6 3s^2 3p^6$.
Note that the $\text{Ca}^{2+}$ ion now has a full octet in its outermost shell (the third shell), which corresponds to the stable noble gas configuration of argon ($\text{Ar}$). This full octet leads to greater energetic stability.
Understand that stability in ions often comes from achieving a noble gas electron configuration, which minimizes energy and increases stability compared to the neutral atom with partially filled outer shells.
Evaluate the incorrect options: the number of protons does not change between Ca and $\text{Ca}^{2+}$, the atomic number remains the same, and $\text{Ca}^{2+}$ actually has fewer valence electrons than Ca, so these do not explain the increased stability.
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