Difference Between Atom and Ion

Main Difference – Atom vs Ion

Atoms are the building blocks of matter. All matter is composed of atoms. Earlier, scientists believed that an atom cannot be further divided. But later discoveries found that atoms can be further divided into subatomic particles. The main subatomic particles are protons, neutrons and electrons. The basic structure that is made out of several atoms is called a molecule. An ion is a derivative of a particular atom. The main difference between an atom and an ion is that atoms have no net electrical charge whereas ions have a net electrical charge.

Key Areas Covered

1. What is an Atom
      – Definition, Basic Features and Examples
2. What is an Ion
      – Definition, Basic Features and Examples
3. What are the Similarities Between Atom and Ion
      – Outline of Common Features
4. What is the Difference Between Atom and Ion
      – Comparison of Key Differences

Key Terms: Anion, Atom, Cation, Electron, Ion, Neutron, Proton

What is an Atom

An atom is the fundamental unit of all matter. In other words, all matter is made out of atoms. Although scientists earlier believed that atoms cannot be further divided, that concept is no longer valid. That concept was changed with the discovery of electron, proton and nucleus. After that, the atomic theory was developed in which the structure of an atom is described.

According to the modern atomic theory, an atom is composed of two components. They are the nucleus and atomic orbitals. The nucleus is composed of protons, which are positively charged subatomic particles, and neutrons, which are neutrally charged subatomic particles. The charge of a proton is +1. Around the nucleus, there is an electron cloud in which the electrons of the atom are in motion along hypothetical orbitals. An electron has a -1 electrical charge. Hence, electrons are negatively charged particles.

Atoms of a certain element are identical to each other. Therefore, the number of protons and neutrons present in the nucleus of atoms are equal for one element. The number of electrons around the nucleus is the same for atoms that belong to the same element.

Protons and neutrons stick together in the nucleus due to the strong forces that exist between these particles. These forces are called interactions. These interactions occur due to the exchange of very tiny particles called mesons. Therefore, in order to break down a nucleus into the protons and neutrons, a very high energy is required. Electrons are in motion around the nucleus. Since electrons are negatively charged; electrons are not attracted to positively charged protons in the nucleus do not fall onto the nucleus since the force that builds up due to the motion of the electron is equal to the force of attraction by the nucleus. Since these two forces balance each other, electrons remain in their motion at a particular distance from the nucleus. The pathway that these electrons move is called a shell or orbital.

Figure 1: Simplified Atomic Structure

The structure of an atom can be given like this, but it is wrong. The actual structure is much more complicated than the above image.

Atoms are able to take part in chemical bonds. Atoms attach together to form molecules or compounds. These attachments occur through chemical bonds. These bonds can be covalent bonds, ionic bonds, coordinate bonds or metallic bonds. In the formation of these bonds, exchange of electrons occur. But the protons and neutrons in the nucleus do not take part in chemical bonding. But in the process of radioactive decay, the nucleus of an atom is converted to a completely different nucleus through conversion of protons or neutrons into different particles along with the emission of radiation.

What is an Ion

An ion is an atom or a molecule that has a net electrical charge. This charge can be either a positive charge or a negative charge. An ion is formed when an atom or a molecule loses or gains electrons. For example, if a particular atom loses an electron, then there aren’t enough electrons to neutralize the total positive charge of the nucleus. Therefore, the whole atom gets a net positive charge. But if an atom gains an electron, then there aren’t enough protons in the nucleus in order to neutralize the total negative charge of all electrons. Therefore, the whole atom gets a net negative charge. Since ions are electrically charged species, these can be attracted by an electrical field. Negative ions are attracted to the positive pole whereas positive charged ions are attracted to the negative pole.

Ions can form ionic bonds. An ionic bond is a type of chemical bond that occurs due to the electrostatic attraction between two ions that are oppositely charged. A negative ion forms ionic bonds with one or more positive ions in order to neutralize the net electrical charge.

Figure 2: Formation of Cations and Anions

Ions are found in two types; cations and anions. Cations are atoms or molecules having a net positive charge whereas anions are atoms or molecules having a net negative charge. Anions and cations are attracted to each other since they are oppositely charged species.

If the ion is a single atom, then it is a monoatomic ion. If the ion is a molecule, then it is a polyatomic ion. Metal atoms often form positively charged ions or cations by removing one or more electrons from the outermost orbital. That is because metal atoms are composed of a less number of electrons in their outermost orbital and are loosely bound to the nucleus. Therefore, these electrons can easily be lost forming a cation than forming an anion by gaining a high number of electrons to fill the orbital. Most of the nonmetals tend to share their unpaired electrons rather than losing or gaining them. But if they tend to become ions, they gain electrons forming an anion rather than becoming a cation by removing a high number of electrons.

Similarities Between Atom and Ion

Atoms can become ions.
Both atoms and ions are composed of electrons that are exchangeable.

Definition

Atom: An atom is the fundamental unit of all matter.

Ion: An ion is an atom or a molecule that has a net electrical charge.

Electrical Charge

Atom: Atoms are neutrally charged.

Ion: Ions are either positively charged or negatively charged.

Attraction to Electrical Field

Atom: Atoms are not attracted to an electrical field.

Ion: Ions are attracted to electrical fields according to their electrical charge.

Number of Electrons

Atom: Atoms are composed of equal numbers of electrons and protons.

Ion: Ions are composed of unequal numbers of electrons and protons.

Conclusion

Atoms are the fundamental unit of all matter with which all matter is made of. Atoms can become ions by either gaining or removing electrons. But not all ions are atoms because there are molecules that can become ions by removing or gaining electrons by that molecule. The main difference between an atom and an ion is that atoms have no net electrical charge whereas ions comprise a net electrical charge.

References:

1. Helmenstine, Anne Marie. “What Is an Atom? (Explanation and Examples).” ThoughtCo. N.p., n.d. Web. Available here. 10 Aug. 2017.
2. ” What is an ion?” BBC. BBC, n.d. Web. Available here. 10 Aug. 2017.

Image Courtesy:

1. “Atom diagram” By The original uploader was Fastfission at English Wikipedia – Transferred from en.wikipedia to Commons by Teratornis using CommonsHelper. (CC BY-SA 3.0) via Commons Wikimedia
2. “Ions” By Jkwchui – Own work (CC BY-SA 3.0) via Commons Wikimedia