What Are Some Examples of Atoms?

Different Types of Atoms

An atom must contain at least one or more protons. Most atoms also have neutrons and electrons.
An atom must contain at least one or more protons. Most atoms also have neutrons and electrons. DAVID PARKER/SCIENCE PHOTO LIBRARY / Getty Images

Atoms are fundamental units of matter that cannot be broken down using any chemical means. Learn what an atom is and get examples of atoms:

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 of protons and neutrons surrounded by a negatively-charged cloud of electrons. At its most basic level, an atom is any matter that contains at least a 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 determines an atom's order in the periodic table, name, symbol, and chemical identity.

Here are some examples of atoms:

  • neon, Ne
  • hydrogen, H
  • argon, Ar
  • iron, Fe
  • calcium, Ca
  • deuterium, usually indicated with D or 2H, which is an isotope of hydrogen that has one proton and one neutron
  • plutonium, Pu
  • F-, which is a fluorine anion
  • protium, an isotope of hydrogen
  • a calcium cation, Ca2+

Atoms Versus Molecules

When atoms bond to each other, they are called molecules. If the chemical symbol of a molecule is written, you can distinguish it from an atom because there will be a subscript following the element symbol that indicates how many atoms are present.

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