Introduction

Substances are broadly divided into physical and chemical. Everything on this planet, from oxygen to water, is made up of atoms combined into fixed proportions. They are represented by their atomic symbols and numbered as per the number of the particular atoms in the substance. For example, water comprises two atoms of hydrogen and one atom of oxygen. Therefore, its symbolic representation is H2O. Similarly, oxygen consists of two oxygen atoms and is represented as O2. 

Every substance with only one kind of atom is known as a molecule, for example, oxygen. Similarly, every substance which has a combination of two or more bits in a fixed proportion is called a compound, for instance, water.

What is a Chemical Formula?

 A chemical formula is the representation of any compound. For example, H2O is the chemical formula of water. 

 Let us discuss a few other substances and their chemical formulae: 

• Carbon dioxide comprises two molecules of oxygen and one molecule of carbon. Hence, the chemical formula is CO2.
• Glucose is made from six molecules of carbon, twelve molecules of hydrogen, and six oxygen molecules. The chemical formula of this compound is C6H12O6. 

A chemical formula remains constant within each substance and cannot be altered. If it is changed, the resultant importance will change. For instance, for every water compound, two hydrogen atoms and one oxygen atom must be combined. This ratio of 2:1 cannot be altered. 

Combining two atoms of hydrogen with two atoms of oxygen results in the formation of hydrogen peroxide.  

These resultant substances formed due to the alteration of any chemical formula will have different physical and chemical properties.  

The other general rule that chemical formulae follow is the rule of whole numbers. Any and every atom that is combined is a whole number. For instance, we cannot form a substance with half oxygen. This is because atoms are indivisible, which means they cannot be divided into halves or quarters and have to be used wholly.

Types of Chemistry Formulae or Chemical Formulae

There are different types of chemical formulae. Following are the basic types of formulas: 

1. Molecular Formula: This chemical formula comprises chemical symbols of the constituent elements and their numerical subscripts. These numbers denote the number of atoms of the constituent elements. A compound’s molecular formula specifies the quantity and specification of atoms in a single molecule.
2. Empirical Formula: The empirical formula reflects the most basic whole-number proportion of ratios of all types of atoms in a compound’s molecule. A compound’s molecular formula can be the same as, or a multiple of, its empirical formula.
3. Structural Formula: The structural formula specifies the number of atoms and their spatial distribution. Although molecular formulae are concise and easy to express, they do not include bonding, atomic arrangement, or atom bonding information. A structural formula is required for that.

Let’s look at a glucose molecule’s molecular, empirical, and structural formulae. 

• Glucose molecular formula: C₆H₁₂O₆. This shows the exact number of carbon, hydrogen, and oxygen constituent atoms written as C, H, and O, respectively. This is the amount seen in one molecule of glucose.
• Glucose empirical formula: CH₂O. This shows the whole number ratio of the respective atoms involved: C, H, and O.
• Finally, the structural formula for glucose will show how each carbon, hydrogen, and oxygen atom in a glucose molecule is bound.  

Laws of a Chemical Combination

 According to the atomic theory proposed by Dalton, there are mainly three rules that every compound must follow to form a substance. These laws are – 

• Conservation of Mass
• Constant Proportions
• Multiple proportions

Chemical Formula for Ionic Compounds 

Cations are listed first in an ionic compound, followed by the anion. The charges above the anionic and cationic sections are crossed above in subscript when composing the formula for an ionic compound. When H+ and PO43- are combined, the charges cross to generate H3PO4. In the case of covalent compounds, the bonding sequence of the compound is maintained. Another case that can be studied is the production of lithium oxide. Lithium-ion with a positive charge passed over oxygen atoms with a negative charge to make Li2O. Here are the rules of writing a chemical formula:

• RULE I: To find the formula for each compound, the valencies of the constituents are cross multiplied. Rule I is implemented in the just mentioned formulations, which is to cross multiply the valencies of the constituents to obtain the formula for the relevant combination.

• RULE II: If a compound contains both metallic and nonmetallic components, the metal’s term or symbol is used first. Magnesium (Mg) is a metal, while chlorine (Cl) is a non-metal; hence, Mg is written before CI.

• RULE III: If a compound comprises polyatomic ions, the ion is placed in parenthesis before the quantity is written to show the ratio. There are no parentheses needed because the number of polyatomic ions is one. However, if the quantity of polyatomic ions is one, no parenthesis is required.

Conclusion

The symbolic representation of any compound is known as a chemical formula. This alphanumeric formula is written using alphabets representing the atoms present in the compound and the numbers representing the number of the particular atom present in that compound. Formulae play an essential role in chemistry as it helps in easy understanding and has a universal representation. It is very feasible to balance and understand the transfer of electrons in a chemical reaction with the help of a chemical formula.