NH4ioneja

NH4ioneja is the Finnish term for ammonium ions, the positively charged species NH4+. Ammonium ions are the conjugate acid of ammonia and are common in aqueous solutions, minerals, and fertilizers. In water, NH4+ coexists with NH3; the equilibrium NH4+ ⇌ NH3 + H+ has a pKa of about 9.25, so NH4+ is the dominant form at pH below about 9.

The ammonium ion is tetrahedral, with four N–H bonds and no lone pairs on nitrogen. The N–H bond length is about 1.03 Å; geometry is ideal Td. In solution it is highly solvated by water via hydrogen bonding.

NH4+ forms salts with many anions, including chloride, nitrate, sulfate, phosphate, and carbonate. Most ammonium salts are highly soluble in water. Thermal decomposition or heating ammonium salts can release ammonia and acid vapors.

In agriculture, ammonium is a major nitrogen source for plants; soil microorganisms convert ammonium to nitrate through nitrification. In animals, ammonia detoxification occurs via the urea cycle; ammonium can be toxic at high concentrations. In chemistry and industry, ammonium salts are widely used as fertilizers, food additives, and in explosives such as ammonium nitrate, and cleaning agents.

Handling NH4+-containing compounds requires care: they can be irritants and, in concentrated forms, harmful if ingested or inhaled. Excess ammonium in water can contribute to eutrophication.