What Are Some Examples of Atoms?

An atom must contain at least one or more protons. Most atoms
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by Anne Marie Helmenstine, Ph.D.
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
Updated January 12, 2019

Atoms are fundamental units of matter that cannot be broken down by any chemical means.

What Makes Something an Atom?

The building blocks of atoms are positively charged protons, neutral neutrons, and negatively charged electrons. Protons and neutrons are similar in mass, while electrons are much smaller and lighter. Many atoms consist of a positively charged nucleus composed of protons and neutrons surrounded by a negatively charged cloud of electrons. At its most basic level, an atom is any particle of matter that contains at least one proton. Electrons and neutrons may be present, but aren't required.

Atoms may be neutral or electrically charged. An atom that carries a positive or negative charge is called an atomic ion.

Atoms of a single element that have different numbers of neutrons from one another are called isotopes.

A single particle of any element listed in the periodic table is an atom. The number of protons present determines an atom's order in the periodic table, along with its name, symbol, and chemical identity.

Here are some examples of atoms:

  • Neon (Ne)
  • Hydrogen (H)
  • Argon (Ar)
  • Iron (Fe)
  • Calcium (Ca)
  • Deuterium, an isotope of hydrogen that has one proton and one neutron
  • Plutonium (Pu)
  • F-, a fluorine anion
  • Protium, an isotope of hydrogen

Atoms Versus Molecules

When atoms bond together, they become molecules. When the chemical symbol of a molecule is written out, you can distinguish it from an atom by the subscript following the element symbol, which indicates how many atoms are present.

For example, O is the symbol for a single atom of oxygen. On the other hand, O2 is the symbol for a molecule of oxygen gas consisting of two oxygen atoms, while O3 is the symbol for a molecule of ozone consisting of three oxygen atoms.