Difference Between Atom and Molecule

The concepts “atom” and “molecule” are part of the terminology that must be mastered when introducing Chemistry and for this same reason it is important that we know the differences between the two terms.  Difference Between Atom and Molecule

ATOM  Difference Between Atom and Molecule

On the one hand, atoms are part of the constituents of matter and range from 0.1 to 0.5 nanometers wide. They are so small that they cannot even be seen with a common microscope.

There are many types of atoms, and each has a unique number, mass, and size. The groupings of atoms of the same type, constitute the chemical elements.

An element is a pure chemical substance that has atoms of the same kind and is distinguished by its atomic number. The atomic number is derived from the number of protons present in the nucleus of the element’s atoms.

So far 118 elements have been discovered and they have been divided into: metals, metalloids and non-metals. Each element has its own set of properties and most are found on earth; while a few have developed from nuclear reactions . All elements can be found in the periodic table, listed according to their atomic number.

The atoms of each element are made up of protons, neutrons, and electrons. Protons and neutrons are found in the nucleus, located in the center of atoms. While the electrons that rotate around, are attached to the nucleus thanks to the electromagnetic force. Electrons have a negative electrical charge and this is why they are attracted to the nucleus, since protons have a positive electrical charge. On the other hand, neutrons have no electrical charge.

Atoms of different elements come together and form molecules. This happens through chemical reactions. For example: two atoms of hydrogen and one of oxygen combine to make a water molecule.


A molecule is the smallest amount of a substance that can exist. It is made up of atoms that are different from each other and for this reason, each of them can be separated. However, these atoms cannot be separated further without causing a nuclear reaction.

Molecules can have very different properties from those of their constituent elements. For example: water behaves very differently from how oxygen and hydrogen behave individually.

On the other hand, a single atom cannot exist independently in nature (without joining something). For example, we will never find a single oxygen atom, it is always attached to something (oxygen = O2). When molecules are formed, they can exist independently in nature; so we can always find a molecule of oxygen, carbon, or water.

The atoms of the molecules are attached to each other in a particular way, depending on the number of bonds that the atom can make. Due to this, the molecules can have hexagonal, pentagonal shapes.

Finally, molecules tend to clump together and their formation depends on their state. For example, in a gaseous state, molecules often fly around. In the liquid state, the molecules tend to be loosely grouped; reason why they can move. Whereas in the solid state, the molecules are tighter or closer together and can only vibrate.

Molecules are generally represented in a molecular formula. For example: C6H12O6 (sugar). Said molecular formula is nothing more than the name of the element, followed by the number of atoms of that element in the molecule.

Key differences between atom and molecule

  • Atoms are constituents of matter, while molecules are made up of atoms different from each other.
  • Atoms are not independently in nature, but molecules can.

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