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What Is an Atom?

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The atom is the basic building block of all matter.

The atom is the basic building block of all matter.

Getty Images This is a basic diagram of an atom, with protons, neutrons and electrons.

This is a basic diagram of an atom, with protons, neutrons and electrons.

AhmadSherif, Wikipedia Commons

Question: What Is an Atom?

The building blocks of matter are called atoms. Yet you may be wondering what, exactly, is an atom? Here's a look at what an atom is and some examples of atoms.

Answer: An atom is the basic unit of an element. An atom is a form of matter which may not be further broken down using any chemical means. A typical atom consists of protons, neutrons and electrons.

Examples of Atoms

Any element listed on the periodic table consists of atoms. Hydrogen, helium, oxygen and uranium are examples of types of atoms.

What Are Not Atoms?

Some matter is either smaller or larger than an atom. Examples of chemical species that are not typically considered atoms includes particles that are components of atoms: protons, neutrons and electrons. Molecules and compounds consists of atoms but are not themselves atoms. Examples of molecules and compounds include salt (NaCl), water (H2O) and ethanol (CH2OH). Electrically charged atoms are called ions. They are still types of atoms. Monoatomic ions include H+ and O2-. There are also molecular ions, which are not atoms (e.g., ozone, O3-).

The Gray Area

Would you consider a single unit of hydrogen to be an example of an atom? Keep in mind, most hydrogen "atoms" do not have a proton, neutron and electron. Given that the number of protons determines the identity of an element, many scientists consider a single proton to be an atom of the element hydrogen.

 

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