Compare cations, anions, and polyatomic ions. What do they all have in common? How are they different?
The correct answer and explanation is :
Comparison of Cations, Anions, and Polyatomic Ions
What They Have in Common:
Cations, anions, and polyatomic ions are all types of ions, meaning they are atoms or groups of atoms with a net electrical charge due to the loss or gain of electrons. Ions form because atoms seek a stable electron configuration, often resembling the nearest noble gas. All these ions participate in chemical bonding, particularly in forming ionic compounds.
Differences Between Them:
- Cations – Positively charged ions that form when an atom loses one or more electrons.
- Example: ( Na^+ ) (Sodium ion), ( Ca^{2+} ) (Calcium ion)
- Typically formed by metals, as they have fewer valence electrons and tend to lose them easily.
- Anions – Negatively charged ions that form when an atom gains one or more electrons.
- Example: ( Cl^- ) (Chloride ion), ( O^{2-} ) (Oxide ion)
- Typically formed by nonmetals, as they have more valence electrons and tend to gain electrons to complete their outer shell.
- Polyatomic Ions – Ions made up of two or more atoms covalently bonded, but carrying an overall charge.
- Example: ( NH_4^+ ) (Ammonium ion, a polyatomic cation), ( SO_4^{2-} ) (Sulfate ion, a polyatomic anion)
- Unlike monatomic ions, polyatomic ions have internal bonding but still interact ionically with other ions.
Explanation (300 Words)
Ions are fundamental to chemistry and exist because atoms seek stable electron configurations. Cations form when an atom loses electrons, resulting in a positive charge. This commonly happens with metals, like sodium (( Na )), which loses one electron to form ( Na^+ ). Anions form when atoms gain electrons, becoming negatively charged. Nonmetals, like chlorine (( Cl )), gain an electron to form ( Cl^- ). These oppositely charged ions attract each other, forming ionic compounds like NaCl (table salt).
Polyatomic ions are unique because they consist of multiple atoms bonded together, yet they carry an overall charge. Unlike monatomic ions (single atoms with a charge), polyatomic ions like sulfate (( SO_4^{2-} )) or ammonium (( NH_4^+ )) act as a unit in chemical reactions. The atoms in a polyatomic ion share electrons covalently, but as a whole, the group has lost or gained electrons, making it an ion.
The key difference among them is that cations and anions are usually single atoms with a charge, while polyatomic ions are groups of atoms with a charge. However, they all share the property of having an electrical charge, which makes them important in forming compounds and conducting electricity in solutions.