AP Chemistry Easy Positive Ions Emergency Memorization

Vocabulary practice for common positive ions, including naming, chemical formulas, and charges based on the AP Chemistry study sheet.

Cation

A positive ion which is formed when an atom has lost electrons.

Subscript

The number of atoms present in a formula; for example, in $NH_4^+$ there are 4 hydrogen atoms.

Superscript

Indicates the charge of an ion; for example, $NH_4^+$ has a charge of $+1$, not $+4$.

hydrogen ion

$H^+$ with a charge of $+1$; also known as an acid proton.

hydronium ion

$H_3O^+$ with a charge of $+1$; represents water + $H^+$.

ammonium ion

$NH_4^+$ with a charge of $+1$; the only positive polyatomic ion in the provided set.

lithium ion

$Li^+$ with a charge of $+1$; part of Group 1.

sodium ion

$Na^+$ with a charge of $+1$; part of Group 1.

potassium ion

$K^+$ with a charge of $+1$; part of Group 1.

silver ion

$Ag^+$ with a fixed charge of $+1$.

magnesium ion

$Mg^{2+}$ with a charge of $+2$; part of Group 2.

calcium ion

$Ca^{2+}$ with a charge of $+2$; part of Group 2.

strontium ion

$Sr^{2+}$ with a charge of $+2$; part of Group 2.

barium ion

$Ba^{2+}$ with a charge of $+2$; part of Group 2.

zinc ion

$Zn^{2+}$ with a fixed charge of $+2$.

aluminum ion

$Al^{3+}$ with a fixed charge of $+3$.

Group 1 ions

Ions that are usually $+1$, including $Li^+$, $Na^+$, and $K^+$.

Group 2 ions

Ions that are usually $+2$, including $Mg^{2+}$, $Ca^{2+}$, $Sr^{2+}$, and $Ba^{2+}$.

Fixed-charge extras

Specific ions with non-group-based fixed charges: $Ag^+$ ($+1$), $Zn^{2+}$ ($+2$), and $Al^{3+}$ ($+3$).

Special multi-atom positive ions

Includes hydronium ($H_3O^+$) and ammonium ($NH_4^+$).