Compounds: A compound is a pure substance similar to an element. However, it represents a combination of two or more elements that are chemically combined in a fixed mass ratio to form a new substance known as a molecule. That is why it is referred to as a chemical compound.

Have you ever thought that table salt is a compound? Yes, table salt is nothing but a sodium chloride compound made up of sodium and chlorine elements combined chemically. To learn more about Compounds, read the below article.

Define Compound

A compound is a pure substance that is composed of atoms of two or more elements, bonded chemically with one another in a definite proportion.

Hence, it can be broken down into simpler substances by only chemical means. The properties of compounds are different from the properties of their constituent elements. The smallest unit of the compound is known as a molecule. Hydrogen element forms maximum compounds in chemistry.

For example, water is represented by the chemical formula \({{\rm{H}}_2}{\rm{O}}\). It contains the elements hydrogen and oxygen in a \({\rm{2:16}}\) or \({\rm{1:8}}\) mass ratio. Water can be obtained from various sources, including rain, rivers, the sea, wells, and lakes. In the pure form of water from any source, the two elements are present in the same fixed ratio, i.e., \({\rm{1:8}}\) by mass. Other examples of compounds include salt, sugar, sand, carbon dioxide, washing soda, chalk, alcohol, etc.

Table Showing Some Common Compounds, Elements Present in them and their Formula

Sl. No.	Compounds	Elements Present	Formulae
1.	Water	Hydrogen and oxygen	\({{\rm{H}}_2}{\rm{O}}\)
2.	Sodium Chloride	Sodium and chlorine	\({\rm{NaCl}}\)
3.	Carbon dioxide	Carbon and oxygen	\({\rm{C}}{{\rm{O}}_2}\)
4.	Sodium bicarbonate	Sodium, hydrogen, carbon and oxygen	\({\rm{NaHC}}{{\rm{O}}_3}\)
5.	Sodium carbonate	Sodium, Carbon and Oxygen	\({\rm{N}}{{\rm{a}}_2}{\rm{C}}{{\rm{O}}_3}\)
6.	Hydrated calcium sulphate	Calcium, Oxygen, Hydrogen, and sulphur	\({\rm{CaS}}{{\rm{O}}_{4 \cdot }}.2{{\rm{H}}_2}{\rm{O}}\)
7.	Magnesium oxide	Magnesium and Oxygen	\({\rm{MgO}}\)
8.	Calcium oxide	Calcium and oxygen	\({\rm{CaO}}\)
9.	Sodium sulphate	Sodium, sulphur, and oxygen	\({\rm{N}}{{\rm{a}}_2}{\rm{S}}{{\rm{O}}_4}\)
10.	Silica	Silicon and Oxygen	\({\rm{Si}}{{\rm{O}}_2}\)
11.	Cane sugar	Carbon, Hydrogen and Oxygen	\({{\rm{C}}_{12}}{{\rm{H}}_{22}}{{\rm{O}}_{11}}\)
12.	Glucose	Carbon, Hydrogen and Oxygen	\({{\rm{C}}_6}{{\rm{H}}_{12}}{{\rm{O}}_6}\)

Types of Compounds

Based on the origin, compounds can be classified into two types. These are organic compounds and inorganic compounds.

1. Inorganic Compounds: Inorganic compounds are those derived primarily from non-living sources such as rocks and minerals.
   A few examples of inorganic compounds are common salt, marble, washing soda, baking soda, carbon dioxide, ammonia, sulphuric acid etc.
2. Organic Compounds: The term organ refers to various organs of living beings. As a result, organic compounds are those derived from living beings, such as plants and animals. Carbon has been discovered to be an essential constituent of all organic compounds. Organic compounds are frequently referred to as carbon compounds.
   A few common organic compounds are: methane, ethane, propane, alcohol, acetic acid, sugar, proteins, oils, fats etc.

Based on the characteristics, compounds are classified into three types. These are acids, bases, and salts.

1. Acids: Acid is a sour chemical compound that forms a water solution that turns blue litmus paper red. Examples of acid include hydrochloric acid, sulphuric acid, nitric acid, citric acid, carbonic acid, lactic acid, etc.
2. Bases: Base is a bitter chemical compound that forms a water solution that turns red litmus paper to blue. Examples of the base include sodium hydroxide, calcium hydroxide, magnesium hydroxide, etc.
3. Salts: Salt is a substance that is produced by the reaction of an acid with a base. Common examples of salts include sodium chloride, calcium chloride, calcium nitrate, zinc sulphate, etc.

Characteristics of Compounds

The important characteristics of the compounds are listed:

1. A pure compound is composed of the same elements combined in a fixed ratio by mass to form molecules: In a compound, the same elements are always present in a fixed ratio by mass, whatever may be its mode of formation.
   For example, in carbon dioxide, carbon and oxygen are present in the ratio of \(3:8\) by mass. This ratio will always be the same regardless of the source of carbon dioxide formation.
   In a compound, the molecules may either be homoatomic (e.g. \({{\rm{H}}_2},{\mkern 1mu} {{\rm{O}}_2},{\mkern 1mu} {{\rm{N}}_2},\), etc.) or heteroatomic (e.g. \({{\rm{H}}_2}{\rm{O}},\,{\rm{C}}{{\rm{O}}_2},\,{{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}\), etc.).
2. A pure compound is homogeneous in nature: A pure compound is a single substance composed of specific elements. Even with the help of a powerful microscope, these cannot be seen.
   For example, in water \(\left( {{{\rm{H}}_2}{\rm{O}}} \right)\), any physical method cannot identify the two elements hydrogen and oxygen. So, we can say that pure compound is homogeneous.
3. A chemical compound is formed by the chemical reaction of the constituent elements: The compound cannot be formed simply by combining the elements. These are combined with each other as a result of some chemical reactions.
   For example, one method for producing carbon dioxide is to burn coke (carbon) in air (a source of oxygen).
   

4. The properties of a compound are altogether different from the elements from which it is formed: Because a compound is formed due to a chemical reaction, its properties are quite different from those of the elements from which it is formed.
For example, hydrogen gas is combustible, whereas oxygen encourages combustion. Water is formed as a result of the chemical reaction between the two gases.

5. Constituents of a chemical compound cannot be separated mechanically: As we all know, a compound is formed due to chemical reaction. Its constituent elements can be separated chemically rather than mechanically.
For example, Water constituents such as hydrogen and oxygen can be separated from water by passing an electric current through it. This is referred to as electrolysis of the water.

6. Formation or decomposition of a compound involves energy change: In the formation of a compound, energy in the form of heat, light, or electricity is either absorbed or evolved.
For example, in the presence of sunlight, hydrogen and chlorine gases combine to form hydrogen chloride gas.

7. A compound has its characteristic melting and boiling points.
For example, Whatever method is used to obtain a sample of pure water, it has melting and boiling points that differ from those of pure hydrogen and oxygen.

Difference between Elements and Compounds

We studied that elements and compounds are both pure substances. Compounds are also made up of elements. Let us distinguish between elements and compounds.

Elements	Compounds
1. An element is made up of one type of atom.	1. A compound can be composed of the same or different atoms. For example, an water molecule, a carbon dioxide molecule, and so on.
2. A physical or chemical method cannot be used to break down an element into anything simpler than it is.	2. The compound’s constituent elements cannot be separated physically but only through appropriate chemical reactions.
3. Elements have their own set of characteristics and properties.	3. The constituent elements of a compound lose their individual characteristics.

Summary

A pure substance composed of atoms of two or more elements bonded chemically with one another in a definite proportion is known as a compound. Compounds can be classified into organic and inorganic compounds based on their origin. Based on the characteristics, compounds are classified into acids, bases, and salts. Carbon dioxide, sucrose, glucose, water are some examples of compounds.

FAQs on Compounds

Q.1. What is an example of a compound?
Ans: Water, carbon dioxide, washing soda, sucrose are some common examples of the compound.

Q.2. What is the classification of compounds?
Ans: Based on the origin, compounds can be classified into two types; these are organic compounds and inorganic compounds.
Based on the characteristics, compounds are classified into three types. These are acids, bases, and salts.

Q.3. How many types of compounds are there?
Ans: There are two types of compounds. They are organic compounds and inorganic compounds.

Q.4. What are the \(3\) types of compounds based on bond?
Ans: The three types of compounds are ionic compound, covalent compound, and coordinate compound.

Q.5. How do we classify compounds?
Ans: Based on the origin, compounds can be classified into two types; these are organic compounds and inorganic compounds.
Based on the characteristics, compounds are classified into three types. These are acids, bases, and salts.