Diammonium dioxido(dioxo)molybdenum, with the chemical formula (NH4)2MoO2(O2), is a chemical compound composed of diammonium ions (NH4+) and molybdenum ions coordinated to two oxide (O2-) ligands. It is commonly known as ammonium molybdate.

Ammonium molybdate is a white crystalline powder that is highly soluble in water. It is an important reagent and precursor in various chemical and industrial applications, including:

1. Laboratory Reagent: Ammonium molybdate is widely used in laboratory settings as a reagent for detecting and quantifying certain elements. It is commonly used in analytical chemistry for the detection of phosphates, silicates, and arsenates.
2. Fertilizer: Ammonium molybdate is used as a source of molybdenum in agricultural fertilizers. Molybdenum is an essential micronutrient for plant growth and plays a vital role in nitrogen fixation and other biological processes.
3. Corrosion Inhibitor: It is used as a corrosion inhibitor in certain industrial applications to protect metal surfaces from oxidation and deterioration.
4. Catalyst: Ammonium molybdate is employed as a catalyst in some chemical reactions, particularly in the conversion of alkenes to epoxides.
5. Pigments and Dyes: It is used in the production of pigments and dyes, including the yellow pigments used in ceramics and paints.

Ammonium molybdate has diverse applications and plays a significant role in various industries, including agriculture, analytical chemistry, and materials science. It is considered a safe compound when handled properly, but, like any chemical, it should be used with appropriate safety precautions in place.