What is the Difference between Atoms Molecules and Ions

Difference between molecules and ions


Our ever-changing society constantly incorporates technical jargon in all forms of multimedia on a daily basis. The immensity of this delivery often confuses many on the simplest of terms. The difference between Molecules and Ions tends to be one of them. Let’s build the definition from the bottom-up.


An atom is thought of as one of the basic units of matter. The simplest way to understand this is if you take any material in the universe and break it down by any possible means, outside of nuclear reactions, you will get the tiniest building blocks. These building blocks are atoms and different types of atoms, in chemistry, are called elements.

Although atoms are considered basic units for most purposes they are not the most fundamental. That is, with modern techniques, we can go smaller. The three to be concerned with are electrons, protons and neutrons. Electrons have a negative charge, protons have a positive charge of the same magnitude as an electron and neutrons have no charge. Nature demands that things have to be neutral to be stable. Each element has a specified number of protons in the nucleus.


In atoms, protons and neutrons are situated at the nucleus and the electrons can be found in distinct orbitals around the nucleus. In simple terms it is analogous to the Solar System. A certain distance away from the nucleus, electrons orbit, the same way a certain distance away Mercury orbits the sun and another distance away Venus orbits, etc…

Instead of just one electron in each orbit nature demands that these electrons exist in numbers of 2 in the first orbital, 8 in the second orbital, 8 in the third orbital and higher numbers in larger orbitals. This is known as the Octet Rule because most of the common elements when this theory was being developed only went up to the third orbital. This rule must be satisfied except in advanced cases beyond this article’s scope.

But an issue arises with a very common element such as Carbon that has 6 protons in its nucleus. Now, remember that nature wants everything that is stable to be electrically neutral and that each element has a specific number of protons in the nucleus which do not move.   But when we split the electrons outside, we see that 2 electrons fill the first orbital but only 4 fill the second orbital for the atom to be neutral. But if it stays neutral then the octet rule will not be satisfied. So there is a problem, for carbon to be neutral it the octet rule must be broken or vice versa and we know carbon exists so what is missing?

The truth is that most elements do not exist just as atoms. Specific atoms share their electrons with each other. This allows the atoms to form an electrically neutral body called a “molecule”. For example, in its outer orbital, Carbon has 4 electrons (called valence electrons) and has 4 empty slots for other electrons. Oxygen however has 6 valence electrons and two empty spots. Two Oxygen atoms will thus share two electrons each with a Carbon atom. The Carbon atom will then share a pair of electrons with each of the Oxygen atoms. There you will have a new, electrically neutral body and satisfies the octet rule called Carbon dioxide or CO2.


Now that we know the difference between atoms and molecules, what makes an ion? It is simple; ions are molecules or atoms that have become non-neutral. That is, they have gained or lost an electron or more to become positively or negatively charged. This however contradicts what was stated earlier that they have to be electrically neutral to be stable. True, ions are unstable unless they are in a medium or in a state where their charge is offset by an opposing charge. Sodium acts as a Cation (positive charge) to the Anion (negative charge) of Chlorine to make sodium chloride or salt. That is, the positive Sodium ion will not exist without the Chlorine ion balancing it and making it neutral. The ions may also exist in water because of its ability to surround and balance individual ions. In other words, ions are another way of nature making atoms and molecules electrically neutral.


Atoms are the basic building blocks of nature.  And nature demands that all stable existence has to be neutral through one method or the other. Because of the Octet Rule, most atoms need to share electrons with each other to become electrically neutral, the resulting combinations are molecules. But atoms can exist as charged units as well as molecules so long as the charge is offset by another means. While in this charged state, they are termed Ions.