Ions and Free Radicals (What’s Difference Between) with Examples

Most people in the world correlate ions and free radicals, but there is a difference between the two. Yes, you read that right. There is a difference between ions and free radicals.

The key difference between free radicals and ions is that free radicals have one or more odd electrons whereas ions have one paired electron. Therefore, free radicals are very unstable while ions are rather stable. So, this is also the main difference between free radicals and ions.

What is the difference between ions and radicals?

Electrons in ions are paired.A radical has at least one unpaired electron.
They are formed due to heterolytic fissionThey are formed due to homolytic fission
Ions are more stable than radicals.Radicals are less stable than ions.

An ion is an atom of an element or a group of atoms of different elements that behave as a single unit with a positive and negative charge on it. Whereas, a radical (often called a ‘free radical’) is an atom of an element or a group of atoms of different elements that have at least one unpaired electron. Radicals are neutral, positive, and negative in charge.

Unlike ions, free radicals have an odd number of electrons. Hence the unpaired electron. This increases the reactivity of free radicals.

Difference between ions and radicals
Difference between ions and radicals

What are the IONS?

The molecule of a chemical compound (usually a salt in solution) is divided into two parts, a positively charged part, and a negatively charged part. These are ions. Cations are called cations and anions are called anions. For example, a molecule of sodium carbonate (Na2CO3) has two parts: sodium (Na+) and carbonate (CO32-). Here sodium is a cation and carbonate is an anion.

Ions can become positively or negatively charged by losing or gaining electrons. An atom or molecule is neutral because the number of protons present in it equals the number of electrons. Therefore, when an atom or molecule loses an electron, a positively charged ion or cation is formed. Similarly, when an atom or molecule gains an extra electron, it becomes a negatively charged ion or anion. Therefore, the number of protons in an ion is never equal to the number of electrons. If the number of protons is high, it becomes a positive ion, and if the number of protons is low, it becomes an anion.

Therefore, from the above, the definition of ion is –

An ion is an atom of an element or a group of atoms of different elements that behave as a single unit with a positive and negative charge on it.

Other than positive and negative, we can also classify ion as –

  • Simple and compound ions
  • Acidic and basic ions

Simple Ions and Compound Ions:

An ion is simple if it consists of a single atom, Na1+, Mg2+, Cl1-, etc. Compound ions, on the other hand, are ions made up of a large number of atoms of various elements. For example, NH41+, SO42-, CO32-, etc. Simple ions are monoatomic, while compound ions are diatomic or polyatomic.

Acidic and Basic Ions:

When salt in a solution splits into two parts, the positive part is called the base ion and the negative part is called the acid ion.

For example, consider the neutralization reaction of potassium hydroxide (base) and hydrochloric acid. Here, the acid reacts with the base to form a salt (potassium chloride) and water. During this salt formation, the base potassium hydroxide contributes a potassium ion (K+). Therefore (K+) is a basic ion. Hydrochloric acid, on the other hand, contributes chloride ions (Cl–). Therefore, (Cl–) is an acidic ion.

Here, some people refer to “simple compound ions” as “simple compound radicals”. Similarly, “acid and base ions” are “acid and base radicals”. There’s a reason for that, which I’ll explain after studying free radicals.

Examples of ions
Examples of ions

What are the RADICALS?

All non-inert gas atoms are chemically unstable. They try to stabilize by using the octet or double rule to bond with other atoms of the same or different elements. However, unpaired electrons can remain in the valence shell of the formed molecule even after bonding with other atoms. Molecules with at least one lone electron in their outermost or valence shell are called free radicals. The presence of this unpaired electron makes free radicals very chemically reactive.

Electrons in atoms occur in pairs, both rotating with opposite spins. This counter-rotation of electrons stabilizes the atom to some extent. However, atoms with an odd number of electrons always have one electron. Therefore, these atoms do not have opposite spins and are therefore less stable than atoms with an even number of electrons. It is important to note here that free radicals always have an odd number of electrons.

In most cases, free radicals have the same number of protons and electrons. Therefore, they are electrically neutral. However, this is not always true. Free radicals can be positively or negatively charged, depending on the presence or absence of excess electrons. This is why people confuse “cations and anions” with “positive and negative radicals”. Charged radicals, also called radical ions, are found mainly in organic compounds.

Therefore, from the above, the definition of radical is –

Radical or ‘free radical’ is an atom of an element or a group of atoms of different elements that have at least one unpaired electron. Radicals are neutral, positive, and negative in charge.

Examples of radicals –

Elemental nitrogen and hydroxyl are the best examples of simple free radicals.

Nitrogen: The atomic number of nitrogen is 7. This means that the nitrogen atom has 7 protons and 7 electrons. Since the number of electrons is odd, there is always one electron. Therefore, nitrogen atoms in a free state are considered radicals. Elemental nitrogen radicals are highly reactive and never exist in the free state of nature.

Hydroxyl: Refer difference between ions and radicals, below.


To understand the difference between ions and free radicals, consider the example of hydroxyl (OH). Hydroxyl ions and hydroxyl radicals are two different types that are often confused. The hydroxyl radical is neutral while the hydroxyl ion has a negative charge.

Heteronuclear fission produces hydroxyl ions, whereas hydroxyl radicals are the result of uniform fission of water molecules. Before learning about hydroxyl ions and hydroxyl radicals, let us understand homogeneous and heterogeneous fission.

Homolytic and Hetrolytic Fission

‘Fission’ means ‘to split. Inhomogeneous fission, the molecules of a compound split so that the atom being split retains one of its original binding electrons. On the other hand, in heteronuclear fission, one of the atoms leaves with both electrons bound. This creates a set of fragments with more electrons than others. The electron-rich fragments have a negative charge and the electron-poor fragments have a positive charge.

Why ions are called radicals?

Image result for What is the Difference between Ions and Free Radicals?

In chemistry, free radicals, also called free radicals, are atoms, molecules, or ions that have at least one valence electron. With few exceptions, these unpaired electrons increase the reactivity of free radicals.

Is free radical the same as anion?

A radical cation is a free radical with a positive charge. Similarly, radical anions are negatively charged free radicals. In other words, radical cations and radical anions are subsets of free radicals.

Are free radicals atoms or ions?

Free radicals are chemical species (atoms, molecules, or ions) that contain one or more unpaired electrons in their outer orbitals and typically exhibit considerable reactivity.

Why free radicals are more reactive than ions?

Free radicals are unstable, short-lived, and highly reactive due to their odd number of electrons. Because of their high reactivity, they can withdraw electrons from other compounds to stabilize them.

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