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Historically, one of the fundamental aspects that chemistry has dedicated itself to investigating is the composition of matter, and at the center of this is the concept of the atom. On the other hand, chemistry also studies the changes that these atoms can undergo, and one of these changes consists of their ionization, that is, their transformation into electrically charged ions.
Due to how similar they are represented on paper, atoms and ions can be confused if care is not taken. That is why, in this article, we will clearly and precisely explore the concepts of atom and ion, learn how to distinguish between them, and then look at a series of examples that will help anyone make this important distinction.
What is an atom?
Atoms are the smallest particles that make up a chemical element. These are extremely small particles formed by a positive nucleus with protons and neutrons, surrounded by a set of negatively charged electrons.
Although the word atom literally means indivisible particle, atoms as we know them today can be divided into any number of subatomic particles. This forces us to specify the definition of the atom as the smallest possible particle that still maintains the composition and properties of a chemical element.
representation of atoms
We represent atoms on paper by the chemical symbol of the element to which they belong. Furthermore, each different element also has a particular name. For example, a hydrogen atom (an element) is represented by the symbol H; cobalt is represented by the symbol Co, and so on.
It is worth highlighting the fact that when we refer to an atom, such as iron, we are referring to the complete atom, with all its protons, neutrons and electrons. This necessarily implies that, when speaking of atoms, we refer to neutral particles.
examples of atoms
Some examples of atoms of different elements are:
| Name | Symbol |
| Lithium | Li |
| Sodium | na |
| Magnesium | mg |
| Iron | Faith |
| Carbon | C. |
| Bromine | br |
| Neon | ne |
What is an ion?
An ion is any discrete chemical species, which may be made up of one or more atoms, and which has a net electrical charge. Said charge can be positive (in which case it is a cation) or negative (in which case it is an anion).
Ions are represented on paper by the element’s chemical symbol (in the case of monatomic ions) or by its formula (in the case of polyatomic ions) and its charge as an exponent in the upper right corner.
The electrical charges of the ions are acquired by loss or gain of electrons. When a neutral atom or group of atoms gains one or more electrons it becomes a negatively charged ion or anion. If, on the contrary, it loses one or more electrons, it becomes a positively charged ion or cation.
Monatomic Ions vs. Polyatomic Ions
As mentioned above, ions can be made up of a single ionized atom, or they can consist of a group of atoms linked together through covalent bonds.
Examples of Ions
The following table presents some examples of both positive and negative ions and both monatomic and polyatomic ions:
| Ion name | Formula | Ion name | Formula |
| bromide anion | Br – | ferric cation | Faith 3+ |
| Nitrate Anion | NO 3 – | ammonium cation | NH4 + _ |
| sodium ion | Nah + | sulfide anion | S 2- |
How to distinguish an atom from an ion
You can tell if something is an atom or an ion both by looking at its formula or symbol and by looking at its name:
in his formula
The most direct way to distinguish atoms from ions is through their formula or symbol. Atoms are species neutral, so one must consist solely of a chemical symbol. This must not have subscripts of any kind that indicate the presence of more than one atom.
If a chemical species is represented by means of a chemical formula, even if it is neutral and made up of only one type of atom, this does not represent an atom, but a molecule.
On the other hand, the presence of an electric charge as an exponent of a chemical symbol immediately indicates that one is in the presence of an ion.
in the nomenclature
Another way to distinguish atoms from ions is by their name. The atoms are called with the same name with which the element of which it is a part is known, nothing more.
Ions, on the other hand, receive very different names. For starters, they usually contain the word ion, anion, or cation at the beginning of the name, which in itself is completely giveaway. On the other hand, the name of the element of which it is a part is almost always modified by means of a system of prefixes and suffixes that indicate the charge of the ion or the valence of the atoms that make up the ion, in the case of polyatomic ions.
References
- Brown, T. (2021). Chemistry: The Central Science (11th ed.). London, England: Pearson Education.
- Chang, R., Manzo, Á. R., Lopez, PS, & Herranz, ZR (2020). Chemistry (10th ed.). New York City, NY: MCGRAW-HILL.
- Flowers, P., Neth, EJ, Robinson, WR, Theopold, K., & Langley, R. (2019). Chemistry: Atoms First 2e . Retrieved from https://openstax.org/books/chemistry-atoms-first-2e/pages/1-introduction
- Planas, O. (2020, October 23). What is an ion? Anions and cations . Retrieved July 21, 2021, from https://energia-nuclear.net/que-es-la-energia-nuclear/atomo/ion
