Definition

1. Noun:
   • The ion NH₄⁺ derived from ammonia: A positively charged polyatomic ion (NH₄⁺) that forms when ammonia (NH₃) gains a proton (H⁺). It behaves chemically in many ways similar to ions of alkali metals like sodium (Na⁺) or potassium (K⁺).

Usage Examples

• Noun:
  • Ammonium is a common constituent in many fertilizers.
  • The compound dissociates in water to release ammonium and chloride ions.
  • Ammonium salts are typically soluble in water.

Advanced Usage

• "Ammonium ion": Often used to specify the ionic form, NH₄⁺, particularly in chemical contexts to distinguish it from molecular ammonia (NH₃).
  • The test detects the presence of the ammonium ion in the solution.

Variants and Related Words

• Ammonia (n): A colorless gas (NH₃) with a pungent smell, which reacts with acids to form ammonium salts.
  • Ammonia is used in cleaning products and as a precursor to ammonium compounds.
• Ammonium compound / Ammonium salt (n): A compound containing the ammonium cation, such as ammonium chloride (NH₄Cl) or ammonium sulfate ((NH₄)₂SO₄).
  • Ammonium nitrate is an important fertilizer.

Synonyms

• NH₄⁺: The chemical formula used as a direct synonym in scientific writing.

Notes on Meaning

The term ammonium almost exclusively refers to the cation NH₄⁺ and its chemical behavior. It is not used to refer to a pure substance but rather to the ionic species present in salts and solutions. Its key characteristic is its resemblance to alkali metal ions, meaning it often forms analogous compounds (e.g., ammonium chloride resembles sodium chloride in some properties).

Noun

1. the ion NH4 derived from ammonia; behaves in many respects like an alkali metal ion