Naming Covalent (Molecular) Compounds

Overview

• Covalent or molecular compounds are made of two non-metals.
• Non-metals are located to the right of the staircase on the periodic table.
• Elements in covalent compounds are held together by covalent bonds in molecules.
• Naming covalent compounds differs from naming ionic compounds (which consist of a metal and a non-metal).

Steps for Naming Covalent Compounds

Step 1: Identify the Elements

• Determine if the compound is made of two non-metals (covalent) or a metal and a non-metal (ionic).

Step 2: Start with the Element Names

• First Element: Use the full element name.
  • Example: For N2O3, the first element is nitrogen.
• Second Element: Use the 'ide' form of the element name.
  • Example: Oxygen becomes oxide.

Step 3: Use Numerical Prefixes

• Indicate the number of atoms using prefixes:
  • 1 - Mono
  • 2 - Di
  • 3 - Tri
  • 4 - Tetra
  • 5 - Penta
  • 6 - Hexa
  • 7 - Hepta
  • 8 - Octa
  • 9 - Nona
  • 10 - Deca
• Apply prefixes to both elements:
  • N2O3 becomes dinitrogen trioxide.

Step 4: Do Not Use Mono for First Element

• Omit 'mono' if the first element has only one atom.
  • Example: CO is carbon monoxide, not monocarbon monoxide.

Step 5: Modify Prefixes to Avoid Awkward Pronunciations

• If a prefix results in 'AO' or 'OO', modify it to 'O'.
  • Example: Cl2O7 is dichlorine heptoxide, not dichlorine heptaoxide.

Examples

• P4S10: Tetra phosphorus decasulfide
• PCl5: Phosphorus pentachloride
• Cl2O7: Dichlorine heptoxide (not heptaoxide)
• P4O6: Tetraphosphorus hexoxide (not hexaoxide)
• CO: Carbon monoxide

Tips

• Pay attention to the element's position in the formula when naming.
• Remember the pronunciation rule to make compound names easier to say.
• Avoid using 'mono' for the first element if only one atom is present.
• Be consistent with the use of prefixes for clarity and accuracy.

By following these guidelines, you can correctly name covalent compounds composed of two non-metals.