Simple categories matching diatomic:

• molecule,
• element,
• system,
• gas,
• substance,
• fluid,
• liquid,
• quantity,

Members with property diatomic:

• nitrogen,
• oxygen,
• liquid_hydrogen,
• sulfur,
• chlorine,
• liquid,
• he,
• hydrogen,
• helium_dimer,
• air,
• fluorine,
• vitreous_silica,
• charge,
• bond_order,
• nitrogen_molecule,
• water,
• helium,
• chlorine_gas,
• diatomic_helium,