What is the Difference Between an Atom and an Ion?

Atoms and Ions

A hand holding up an artistically represented atom
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Atoms are the smallest unit of matter that can't be broken down chemically. Molecules are groups of two or more atoms that are chemically bonded. Ions are atoms or molecules that have gained or lost one or more of their valence electrons and therefore have a net positive or negative charge.

An atom can be an ion, but not all ions are atoms. There are distinct differences between an atom and an ion.

What Is an Atom?

An atom is the smallest possible unit of an element. Atoms are considered to be the basic building blocks of matter because they cannot be divided into smaller particles by any chemical process. Atoms are considered to be the basic building blocks of matter because they cannot be divided into smaller particles by any chemical process.

An atom consists of three types of subatomic particles: neutrons, protons, and electrons. Neutrons and protons are both located in the nucleus of the atom; neutrons are neutrally charged particles, and protons are positively charged particles. Electrons are negatively charged particles which orbit the nucleus of the atom. Their arrangement and movement are the basis for many of the chemical properties of the element.

Each type of atom is assigned an atomic number which tells the number of protons in the atom. Normally, an atom has the same number of positive particles (protons) and negative particles (electrons). So the number of protons is identical to the number of electrons, and both are identical to the atomic number.

What Is an Ion?

Ions are atoms with extra electrons or missing electrons. When an atom's outermost orbital gains or loses electrons (also known as valence electrons), the atom forms an ion. An ion with more protons than electrons carries a net positive charge and is called a cation. An ion with more electrons than protons carries a net negative charge and is called an anion. The number of neutrons doesn't come into play since they are electrically neutral. Changing the number of neutrons determines the isotope.

Ions are often formed in nature when static electricity draws electrons away from atoms. When you experience an electrical shock after touching a doorknob, you have released a stream of electrons, thus creating ions.

What Are the Properties of Ions?

In addition to being positively or negatively charged, ions can quickly bond with ions with the opposite charge. Some common compounds are made up almost entirely of chemically bonded ions. For example, salt is made up of a repeating series of chloride anions and sodium cations.

Other examples of important ions include electrolytes, such as chloride, potassium, magnesium, and calcium ions which are essential to health. Electrolytes in sports beverages help to hydrate the body. Potassium ions help to regulate heart and muscle functions. Calcium is critical for bone growth and repair, and it also plays a role in supporting nerve impulses and blood clotting.