Molecules of Compounds and Concept of Ions

What are Compounds?

A Compound is simply two or more elements combined in a fixed proportion. In simple words, every compound is made up of molecules; and molecules are made up of different atoms in a fixed proportion.

Compounds

For example, 2 hydrogen atoms and 1 oxygen atom come together to give 𝐻2𝑂, that is 1 molecule of the compound water. This means that in a water molecule, the ratio of hydrogen and oxygen will always be 2:1.

Water molecule

Here are a few more examples of atoms of different elements combining in a fixed proportion to give a molecule of a specific compound.

Examples of molecules of compounds

What are Ions?

An atom or group of atoms that carries a positive or negative electric charge as a result of having lost or gained one or more electrons are called Ions.

A positively charged ion is called a Cation and a negatively charged ion is called an Anion.

When a cation and an anion come closer, they attract each other and get bonded. This bonding leads to the formation of a molecule. Usually, with the formation of such a molecule, the net charge on it is neutral.

Many such similar molecules come together to form a compound.

Formation of compound

For example, when positively-charged sodium cations and negatively-charged chlorine anions get attracted towards each other, they form a very strong bond which gives us sodium chloride, that is NaCl.

Formation of NaCl

What are Polyatomic ions?

A polyatomic ion is an ion composed of more than one atom. So, it is a unit having more than one atom and carries a charge. It can be positive or negative, but not neutral.

For example, the ammonium ion consists of 1 nitrogen atom and 4 hydrogen atoms. Together, they comprise a single ion with a 1+ charge and a formula of 𝑁𝐻4 +.

NaC

What are Chemical formulae?

In all the examples of molecules discussed thus far, there is a specific way of representing them. This is the chemical formula of the compound.

Chemical formulae are the representation of the number of atoms of particular elements that are present in a particular compound.