Multiple Choice
Which type of elements typically form anions?
1
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2. Atoms & Elements
Ions
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Which of the following ions has the greatest charge density?
A
K^{+}
B
Al^{3+}
C
Na^{+}
D
Mg^{2+}
Verified step by step guidance1
Understand that charge density is defined as the charge of an ion divided by its size (volume or radius). In simpler terms, it reflects how concentrated the charge is on the ion's surface.
Recall that charge density increases with higher charge and decreases with larger ionic radius. So, ions with higher positive charge and smaller size have greater charge density.
List the ions given: $K^{+}$, $Al^{3+}$, $Na^{+}$, and $Mg^{2+}$. Note their charges and relative sizes. Typically, ionic radius decreases across a period and increases down a group in the periodic table.
Compare the charges: $Al^{3+}$ has a charge of +3, $Mg^{2+}$ has +2, and $K^{+}$ and $Na^{+}$ have +1. Then compare their sizes: $Mg^{2+}$ is smaller than $Na^{+}$ and $K^{+}$ because it is higher in the periodic table and has a higher charge pulling electrons closer.
Conclude that $Mg^{2+}$, with a relatively high charge and smaller ionic radius compared to the others, has the greatest charge density among the ions listed.
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