Multiple Choice
Which of the following best describes the difference between cations and anions?
1
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2. Atoms & Elements
Ions
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Which of the following ions has the same electron configuration as the noble gas neon?
A
Cl^−
B
K^+
C
Na^+
D
Mg^{2+}
Verified step by step guidance1
Recall that the noble gas neon (Ne) has the electron configuration $1s^2 2s^2 2p^6$, which corresponds to a total of 10 electrons.
Determine the number of electrons in each ion by considering the atomic number and the charge of the ion:
- For $\mathrm{Cl}^-$: Chlorine has atomic number 17, so neutral Cl has 17 electrons. The negative charge means it has gained 1 electron, totaling 18 electrons.
- For $\mathrm{K}^+$: Potassium has atomic number 19, so neutral K has 19 electrons. The positive charge means it has lost 1 electron, totaling 18 electrons.
- For $\mathrm{Na}^+$: Sodium has atomic number 11, so neutral Na has 11 electrons. The positive charge means it has lost 1 electron, totaling 10 electrons.
- For $\mathrm{Mg}^{2+}$: Magnesium has atomic number 12, so neutral Mg has 12 electrons. The 2+ charge means it has lost 2 electrons, totaling 10 electrons.
Compare the total electrons of each ion to neon's 10 electrons. The ions with 10 electrons have the same electron configuration as neon.
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