Which of the following species has 10 electrons? (Atomic numbers: Na = 11, Mg = 12, Al = 13, Cl = 17)
ANa
BMg$^{2+}$CORRECT
CCl$^-$
DAl
JUPEBChemistryAtomic Structure and Periodicity
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Why the answer is B, and why the others tempt you.
Mg has 12 electrons; losing two gives Mg$^{2+}$ with 10, the configuration of neon. Na and Al have 11 and 13 electrons, and Cl$^-$ has 18.
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