Chemical Formulas

Chemical formulas are used to express the composition of molecules and ionic compounds in the terms of chemical symbols.

• Molecular formulas give the exact number of atoms of each element in a molecule
  • Structural formula: this formula will show how atoms are bonded to one another in a molecule     
• Empirical formulas show the types of elements present and the simplest ratios of the different kinds of atoms.

Atoms of most elements will interact to form compounds. The compounds are classified as two types:

• Molecular compounds
• Ionic compounds
• Ionic compounds are made of anions (negative ions) and cation (positive ions).

Naming and Writing Formulas for Ionic Compounds

• The name of a binary ionic compound will have the cation name followed by the anion name.
• As for writing the formula for a binary ionic compound, write down the symbol for the cation and then the anion. Then balance the charges.

Naming and Writing Formulas for Molecular Compounds

• Prefixes will show how many atoms of each element are present in a molecule of a binary compound.
• As for writing the formula for a binary molecular compound, write the symbols for the elements and use the prefixes to determine the subscripts.

Chemical Formulas - Back to Chemistry Help
Go Back to SG Learn Online