We have studied about atoms, molecules, ions, cations, anions, and various other terms in our chemistry lectures. Chemistry is concerned with how the matter is produced. The substances, their properties, and reactions come under chemistry. These substances also include atoms and molecules. Now, you must be wondering what atoms and molecules are.

Atom

Atoms are defined as the smallest molecules that can be divided in order to form a chemical element. Atoms are very tiny and are present in solid, liquid, and gases. Atoms consist of electrons and nuclei. Further, the nucleus consists of neutrons and protons. It is interesting to note that the electrons present in the atoms are attracted by the protons present in nuclei through a strong electromagnetic force.

Now, with atoms comes the atomic number. The atomic number is defined as the protons present in the nucleus. The number of protons that are present in the chemical elements equals the atomic number. We have often seen that several chemicals have their atomic numbers. For instance, the atomic number of chlorine is 17, the atomic number of sodium 23, etc.

Molecules

On the other hand, molecules are defined as the group of atoms that form several units so that the pure substances can be divided. These pure substances/ chemicals are able to maintain their chemical properties. A molecule is the smallest unit of a compound. Well, there are several points of contrast between atoms and molecules. So, let us discuss them.

S.N	ATOMS	MOLECULES
1.	Atoms are the smallest part of molecules that can be divided in order to form a chemical element.	On the other hand, molecules are defined as the group of atoms that form various small units in order to divide the pure substances.
2.	Atoms are the smallest part of an element.	Molecules include a group of two or more atoms combined together.
3.	The structure of an atom can be described as a tiny particle, along with various properties.	The structure of molecules can be described as the joint or combined group of atoms.
4.	Atoms are not able to remain stable due to the electrons. These electrons are present in the outer shells, due to which the atoms are unstable.	As stated above, molecules are the combined group of atoms. Therefore, molecules have that stability, unlike atoms.
5.	Atoms are made up of three elements, namely electrons, neutrons, and protons.	Molecules comprises of the same or different groups of atoms.
6.	Atoms show a certain level of reactivity, i.e., they react with the elements to form a chemical bond.	On the other hand, molecules do not possess such reactive nature.
7.	There are various kinds of atoms like radioactive, ions, antimatter, and isotopes.	Different types of molecules include diatomic molecules, hetero-nuclear diatomic molecules, and homo-nuclear diatomic molecules.
8.	Examples: Oxygen (O) Sulphur (S) Phosphorous (P) Hydrogen (H)	Examples: Oxygen (O2) Water (H2O) Sulphur (S8) Phosphorous (P4)

So, these are some points of contrast regarding the molecules and atoms. Atoms are molecules that differ from one another in various aspects. Now, a question arises here, i.e., can atoms be considered as a molecule? Well, that is not true. Molecules are different from atoms. Atoms are small and are considered complex in nature. Therefore, we cannot call atoms and molecules as interdependent. They vary from each other.

As mentioned in the table, there are several types of molecules and atoms. So, let us discuss the significant kinds.

Types of Molecules

1. Diatomic Molecule: As the name suggests, a diatomic molecule comprises of two atoms. The atoms can be made up of the same or different elements. Examples of diatomic molecules include O2, CO, etc.

2. Heteronuclear Diatomic Molecule: Hetero-nuclear diatomic molecule is defined as the molecules consisting of two atoms having the same elements. There are seven elements included, namely:

• Hydrogen (H2)
• Oxygen (O2)
• Nitrogen (N2)
• Fluorine (F2)
• Chlorine (Cl2)
• Iodine (I2)
• Bromine (Br2)

These elements are found in every chemical bond and have a strong reactive nature.

3. Homo-nuclear Diatomic Molecules: In a homo-nuclear diatomic molecule, two atoms have different elements. These elements are chemically combined with one another. Examples of homo-nuclear diatomic molecules include:

• Carbon Monoxide
• Hydrochloric Acid (HCl)
• Hydrogen Fluoride (HF)

So, these are the major types of molecules. Now, let us discuss the various types of atoms as well.

Types of Atoms

1. Ions: Ions are defined as the missing or extra electrons present in an element. Ions can have a negative or a positive effect on many chemical reactions.
2. Antimatter: Antimatter is defined as the atom having a twin particle with a contrary, electric charge. These kinds of atoms are often produced in laboratories. These atoms are very fragile and comprise of an anti-electron and an anti-proton. These atoms are rarely found anywhere.
3. Radioactive: When an atom is unstable, it is called a radioactive atom. This instability is formed when the nucleus has many neutrons. In such situations, the atoms release particles until they attain stability.
4. Isotopes: Every atom is made up of hydrogen, chlorine, or iron elements. These elements have their counterparts known as isotopes. Isotopes include various neutrons. But the amount of neutrons is stabilized in isotopes to prevent it from becoming radioactive.

So, these are the significant kinds of atoms. Both atoms and molecules are tiny particles that help in the formation of a chemical element. Now, atoms and molecules possess some characteristics. So, let us look at them.

Characteristics of Atoms

• Atoms are small in size, but their sizes vary with the size of the nucleus.
• The atomic mass of an element is present in the nucleus.
• The three major elements of atoms are neutrons, protons, and electrons. All atoms comprise these three elements.
• Atoms are held together with a strong electromagnetic force.
• The nuclear force holds the nucleus..
• Atoms consist of the atomic number.
• Ions, radioactive, antimatter, etc., are the significant types of atoms.

Characteristics of Molecules

• The water solubility in molecules is variable.
• The boiling temperatures at which molecules are melted are very low.
• The electrical conductivity of molecules is poor.
• The solid form of a molecule is soft.
• Molecules have spaces between them.
• Molecules move in constant motion.
• Molecules attract each other and are combined in a group of particles.
• Molecules are small in size.

So, these are some of the characteristics of atoms and molecules. Atoms and molecules are the major components of an element. These chemical compounds consist of tiny atoms and molecules. Atoms consist of an atomic number, but molecules do not have such numbers. Thus, atoms and molecules differ in several aspects.