Monatomic
Definition and meaning of Monatomic in chemistry.
Monatomic describes a substance or particle that consists of a single atom rather than multiple bonded atoms. Noble gases and single-atom ions are the most common examples of monatomic species.
In more detail
Monatomic substances contrast sharply with polyatomic species, which contain two or more atoms bonded together. The six noble gases (helium, neon, argon, krypton, xenon, and radon) are naturally monatomic because they are chemically inert. Monatomic ions, like sodium (Na+) and chloride (Cl-), are equally important in chemistry, while most other elemental gases form diatomic molecules like N2 or O2 rather than remaining monatomic. The monatomic/polyatomic distinction is fundamental to understanding molecular composition and chemical reactivity.
Key facts
| Field | General Chemistry |
|---|---|
| Opposite | Polyatomic |
| Natural examples | Noble gases (He, Ne, Ar, Kr, Xe, Rn) |
| Also applies to | Monatomic ions like Na+, Cl-, Al3+ |
Helium gas (He) is monatomic, consisting of individual helium atoms; it never forms clusters or bonds with other atoms under ordinary conditions.
Frequently asked questions
Is oxygen ever monatomic?
Oxygen atoms can exist as monatomic oxygen (O) in high-energy environments like the upper atmosphere and plasmas, but under normal conditions oxygen exists as diatomic O2 gas.
What is a monatomic ion?
A monatomic ion is an ion consisting of a single atom that has gained or lost electrons, such as Na+ (sodium cation) or Cl- (chloride anion).