About this dataset
A monatomic substance consists of individual atoms, while a diatomic molecule contains two bonded atoms. The familiar elemental diatomic molecules are hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine. They are often remembered as H₂, N₂, O₂, F₂, Cl₂, Br₂, and I₂.
The noble gases are the standard monatomic examples because their filled outer electron shells make isolated atoms comparatively stable. The table combines these classroom reference sets with identifiers and structure strings that can be reused in chemical software.
Why some elements are diatomic
For the seven commonly taught diatomic elements, pairing two atoms produces a more stable electronic arrangement than keeping the atoms separate under ordinary conditions. This does not mean that every two-atom molecule is an element: carbon monoxide and hydrogen chloride are also diatomic, but each contains two different elements.
State matters too. Bromine is a liquid and iodine is a solid near room temperature, yet their elemental forms are still Br₂ and I₂. “Diatomic” describes the number of atoms in the molecule, not its physical state.
How to use the list
Use the classification column to separate elemental diatomic molecules from monatomic elements and other two-atom species. Formula identifies composition, while SMILES and PubChem CID provide machine-readable and database-ready references.
How this dataset was assembled
The starter list separates stable elemental diatomic molecules from monatomic noble gases. PubChem supplies compound identifiers where available, while NIST is cited for reference data on selected diatomic species.
Each row retains source identifiers where available. Molecular weight is calculated from the recorded formula, and the original names, structures, classifications, and database links remain visible so individual entries can be checked before reuse.
People also ask
What are the seven diatomic elements?
Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine occur as H₂, N₂, O₂, F₂, Cl₂, Br₂, and I₂ in their familiar elemental forms.
How can you tell whether an element is monatomic or diatomic?
Check its stable elemental form under the conditions being discussed. Noble gases are normally represented as individual atoms, whereas the seven elemental diatomics are represented with a subscript 2.
Are all diatomic molecules gases?
No. Hydrogen, nitrogen, oxygen, fluorine, and chlorine are gases near room temperature, but bromine is a liquid and iodine is a solid.
Is carbon monoxide a diatomic molecule?
Yes. CO is a heteronuclear diatomic molecule because it has two atoms from different elements. It is not one of the seven elemental diatomic molecules.
Sources and further reading
- PubChem — Canonical compound identifiers, names, formulas, structures, SMILES, and downloadable compound records.
- NIST Chemistry WebBook — Reference physical chemistry data and diatomic constants for selected species.
- OpenStax Chemistry — Chemistry definitions used for educational polarity, bonding, organic chemistry, and molecule-class explanations.