Binary Molecular Compounds

Binary Molecular Compounds

This article covers the information related to the rules for naming binary molecular compounds.
When two non-metal elements combine, they form a binary molecular compound. These compounds combine by forming a covalent bond between the non-metallic elements. Some of the common examples include H2O, NaCl, MgCl, CO, etc. As they do not form ionic bonds, it becomes difficult to name them according to their electrical neutrality. These compounds may have a generic name, as well as systemic names. They can exist in all three states (solid, liquid and gaseous) under standard temperature and pressure (STP). They have low melting and boiling points. We generally tend to use the common nomenclature for most of the compounds, like water and salt. According to the International Union of Pure and Applied Chemistry (IUPAC), the rules for naming these compounds are explained below.

Rules for Naming

Rule # 1: The element with the lowest group number is written first followed by the element with a higher group number. The exception to this rule is only if the compound contains an oxygen and a halogen. In this case, the name of the halogen is written first when naming the binary compound.

Rule # 2: When both the elements belong to the same group, the element with the higher period number is written before the one with the lower period number.

Rule # 3: When writing the name of the second element, a suffix -ide is added to the name.

Rule # 4: The number of atoms in each of the non-metal elements present in the chemical formula of the compound are indicated using Greek prefixes. The exception to this rules is that the prefix mono is generally not used when the compound contains just one atom. The following is the list of prefixes used during the nomenclature.
  • 1 ~ mono-
  • 2 ~ di-
  • 3 ~ tri-
  • 4 ~ tetra-
  • 5 ~ penta-
  • 6 ~ hexa-
  • 7 ~ hepta
  • 8 ~ octa-
  • 9 ~ nano
  • 10 ~ deca-
Binary Molecular Compounds List

Binary Molecular Compounds List
CompoundSystemic Name
CO2Carbon dioxide
COCarbon monoxide
Cbr4Carbon tetrabromide
Ccl4Carbon tetrachloride
As2O5Diarsenic pentoxide
H2SDihydrogen monosulfide
H2ODihydrogen monoxide
N2ODinitrogen monoxide
N2H4Dinitrogen tetrahydride
N2O4Dinitrogen tetraoxide
P2O5Diphosphorus pentoxide
S2F10Disulfur decafluoride
Icl4Iodine trichloride
NO2Nitrogen dioxide
NONitrogen monoxide
NF3Nitrogen trifluoride
NH3Nitrogen trihydride
NI3Nitrogen triiodide
Pcl5Phosphorous pentachloride
Pcl3Phosphorous trichloride
PH3Phosphorous trihydride
Pbr5 Phosphorus pentabromide
SeF6Selenium hexafluoride
SiO2 Silicon dioxide
SO2Sulfur dioxide
SF6Sulfur hexafluoride
SO3Sulfur trioxide