What is a molecule in chemistry? Eduinput

Molecules are the smallest units of substance that can exist independently.

These are very important for the survival of any living organism. The human body contains millions of molecules and each molecule is a very small particle.

The molecule is the smallest particle of a pure substance that can exist independently. It may consist of two or more atoms.

Here are the molecules examples…

For exampleH₂,H₂O, CO₂, C₆H₁₂O₆ etc.

Why molecules can exist independently?

Molecules can exist independently because molecules are formed by the combination of atoms. Actually, atoms react together to attain noble gases’ electronic configuration.

Noble gases are stable because their outermost shells are complete. In another word, noble gases obey the duplet and octet rule. So when a molecule is formed it becomes stable and exists independently.

What are molecules made of?

Molecules are formed when the electrons of the element are separated and they become stable. They are made up of two or more atoms bonded together. The atoms bond together through the electrons present in each atom.

The number of electrons in a particular atom is termed valence. The valence determines the types of bonds that are formed between atoms. The different kinds of bonds in molecules are covalent, ionic, and metallic. The number of bonds that are present depends upon the nature of the atoms present.

What is duplet rule?

Attaining of two electrons in the outermost shell of an atom is called the duplet rule.

For example, Helium obeys the duplet rule. The atomic number of helium is two. It contains two electrons in its outermost shell.

What is octet rule?

Attaining eight electrons in the outermost shell of an atom is called the octet rule.

 For example, Neon obeys the octet rule. The atomic number of neon is ten. It means that neon contains two electrons in the first shell and eight electrons in the outermost shell.

What is atomicity?

The number of atoms present in a molecule is called its atomicity.

The atomicity of carbon dioxide (CO2) is three because carbon dioxide contains three atoms in its molecule. Similarly the atomicity of NH3, CH4, and C₆H₁₂O₆is respectively 4,5 and 24.

Classification of molecules

Molecules are classified into three categories on the basis of atomicity, nature, and size. Let us explain them one by one.

1. On the bases of atomicity (number of atoms)
2. Mono atomic molecules

Those molecules which contain only one atom are called mono-atomic molecules.

For example He, Ne, Ar, Kr,Xe etc.

Further, the ones based on the number of atoms per molecule are Diatomic, Triatomic, and Tetratomic molecules.

Poly atomic molecules

Those molecules which contain many atoms are called polyatomic molecules.

For example C₆H₁₂O_6, C₁₂H₂₂O₁₁etc.

• On the bases of the Nature of atoms
• Homo atomic molecules

Those molecules which consist of atoms of the same element are called homo atomic molecules.

For example H₂, Cl₂, O₃, P₄, S₈ etc.

Hetero atomic molecules

Those molecules which consist of atoms of different elements are called heteroatomic molecules.

For example H₂O, CO₂, C₆H₁₂O₆ etc.

On the bases of the Sizes of molecules

Micromolecules

Those molecules which are small in size are called micromolecules.

For example O_3, H₂O, CO₂, C₆H₁₂O₆ etc.

Macromolecules

Those molecules which are large in size are called macromolecules.

For example Hemoglobin, Diamond Graphite, etc.

What is hemoglobin molecule?

• It is a blood protein.
• It helps to carry oxygen from our lungs to all parts of our body.
• The elements present in hemoglobin are C,H,O,N along with Fe.
• Each molecule of hemoglobin is made up of nearly 10,000 atoms.
• Each hemoglobin molecule is 68,000 times heavier than a hydrogen atom.

Molecules are also categorized on the basis of dissolving properties. For example polar and non-polar molecules.

What do polar and non-polar mean?

In simple terms, polar means oppositely charged, and non-polar means equally charged. To understand the difference between polar and non-polar bonds, it is essential to comprehend electronegativity. 

What are polar molecules?

Molecules that are formed when atoms with different electronegativities share electrons to form a covalent bond. Polar bonds have a high melting point, boiling point, and low vapor pressure. Polar molecules interact with other polar substances.

Polar molecules are soluble in polar solvents like water. These molecules have positive and negative charges on opposite ends. Therefore, they are electrically charged. Examples: hydrochloric acid.

What are non polar molecules?

Non-polar molecules are formed when two atoms share electrons evenly, a type of chemical bond known as a non-polar covalent bond is created.

Non-polar molecules are soluble in non-polar solvents like carbon tetrachloride.  Non-polar bonds have low melting points, boiling points, and high vapor pressure. Examples: Hydrogen.