C

Cation

M^n+
Quick Reference
Formula / NotationM^n+
Also Known AsPositive ion, metal ion (when from metal), electrophilic ion

What is Cation?

A cation is a positively charged ion formed when an atom or molecule loses one or more electrons. Cations are attracted to the negatively charged cathode during electrolysis. Metals typically form cations. Common cations include sodium (Na⁺), calcium (Ca²⁺), iron(III) (Fe³⁺), and ammonium (NH₄⁺). Cation size generally decreases with increasing charge for the same element.

Formula & Notation

M^n+

Other Names / Synonyms: Positive ion, metal ion (when from metal), electrophilic ion

Properties & Characteristics

A cation is a positively charged ion formed when an atom or molecule loses one or more electrons. Cations are attracted to the negatively charged cathode in electrolysis. Metal cations result from ionisation of metallic elements. Polyatomic cations include ammonium (NH₄⁺) and hydronium (H₃O⁺). Cation size is generally smaller than the parent neutral atom because losing electrons reduces electron-electron repulsion and allows greater nuclear attraction.

Uses & Applications

Cations are essential components of ionic compounds, electrolyte solutions, and biological systems. Na⁺ and K⁺ regulate nerve impulses; Ca²⁺ is crucial for bone structure and muscle contraction; Fe³⁺/Fe²⁺ is central to haemoglobin and enzyme function. Metal cations are the active sites in many industrial catalysts.

Safety Information

Cation toxicity varies widely: Na⁺ is essential, Pb²⁺ and Hg²⁺ are highly toxic heavy metal cations. Many transition metal cations cause skin and respiratory sensitisation. Consult the SDS for any specific ionic compound before handling.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Cation
Formula M^n+
Synonyms Positive ion, metal ion (when from metal), electrophilic ion

Frequently Asked Questions

A cation is a positively charged ion formed when an atom or molecule loses one or more electrons. Cations are attracted to the negatively charged cathode during electrolysis. Metals typically form cations. Common cations include sodium (Na⁺), calcium (Ca²⁺), iron(III) (Fe³⁺), and ammonium (NH₄⁺). Cation size generally decreases with increasing charge for the same element.

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