Chemical Formula expresses the amount (proportions) of atoms that form a particular compound, by using a single line of symbols, numbers and plus(+) and minus (−) signs. These may include subscripts and superscripts. Chemical formula should not be misunderstood as a chemical name, and it contains no words. A Chemical formula may give certain simple chemical structures. Chemical formulas are more limiting than chemical names and structural formulas.
There are certain types of Chemical Formulas:
1.) Empirical Formulas:
Empirical Formulas are the simplest type of Chemical Formulas; these use only letters and numbers indicating atomic proportional ratios (the number of atoms of one type to those of other types). This is the simplest ratio.
2.) Molecular Formulas:
Molecular Formulas indicate the simplest numbers of each type of atom in a molecule of a molecular substance, and thus they are sometimes the same as empirical formulas (generally for molecules that only have one atom of a particular type), and at other times require larger numbers than do empirical formulas.
Difference between molecular and Empirical Formula:
An example for the difference is Glucose, which is CH2O, while its molecular formula requires all atoms to be multiplied by a factor of six, giving C6H12O6.
3.) Condensed Formulas:
Sometimes a chemical formula is made complicated by being written as condensed formulas which provide additional information about the particular ways in which the atoms are chemically together, either in covalent or ionic bonds, or various combinations of both. This is possible if the relevant bonding is easy to show in one dimension.
An example is the condensed molecular for ethanol, which is CH3-CH2-OH or CH3CH2OH. Thus even a condensed chemical formula is limited in its ability to show complex bonding relationships between atoms, especially atoms that have bonds to four or more different substituent’s.
Limitations of Chemical Formulas :
Since a chemical formula must be expressed as a single line of chemical element symbols, it is often cannot give much information as a true structural formula, which is a graphical representation of the spacial relationship between atoms in chemical compounds.