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. 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