Multiple Choice
Which of the following best describes a cation and its typical location on the periodic table?
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2. Atoms & Elements
Ions
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Which of the following ions has the same electron configuration as a noble gas?
A
Cl^+
B
O^2+
C
K^+
D
Na^+
Verified step by step guidance1
Recall that noble gases have completely filled electron shells, which correspond to very stable electron configurations. To determine if an ion has the same electron configuration as a noble gas, we need to compare the electron count of the ion to that of the nearest noble gas.
Write the electron configuration of the neutral atom first, then adjust for the charge of the ion by adding or removing electrons accordingly. For example, for Cl (chlorine), which has 17 electrons, Cl^+ means one electron is removed, so it has 16 electrons.
Determine the electron count for each ion: Cl^+ has 16 electrons, O^2+ has 6 electrons (8 - 2), K^+ has 18 electrons (19 - 1), and Na^+ has 10 electrons (11 - 1).
Identify the noble gas electron configurations closest to these electron counts: Neon (Ne) has 10 electrons, Argon (Ar) has 18 electrons, and so on. Then check which ion's electron count matches a noble gas.
Conclude which ion has the same electron configuration as a noble gas by matching the electron count and configuration. For example, Na^+ with 10 electrons matches the electron configuration of Neon, a noble gas.
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