Which element forms a 3+ ion?

Which element forms a 3+ ion?

• A. Al 3+
• B. Ca 2+
• C. Cu 2+
• D. Ag+

Answer: (A)

When atoms form ions, they lose electrons to reach a stable electron arrangement. Aluminium has three electrons in its outer shell that it can lose, so it most readily forms a positive ion with a 3+ charge, Al3+. This mirrors the pattern that elements in the same group tend to lose a number of electrons equal to their group number, reaching a noble-gas configuration. Calcium, in contrast, loses two electrons to form Ca2+. Copper commonly forms Cu2+ (and can also form Cu+), but not a 3+ ion in ordinary chemistry. Silver tends to form Ag+ by losing one electron. So aluminium is the one that forms a 3+ ion.

When atoms form ions, they lose electrons to reach a stable electron arrangement. Aluminium has three electrons in its outer shell that it can lose, so it most readily forms a positive ion with a 3+ charge, Al3+. This mirrors the pattern that elements in the same group tend to lose a number of electrons equal to their group number, reaching a noble-gas configuration.

Calcium, in contrast, loses two electrons to form Ca2+. Copper commonly forms Cu2+ (and can also form Cu+), but not a 3+ ion in ordinary chemistry. Silver tends to form Ag+ by losing one electron. So aluminium is the one that forms a 3+ ion.