Atom Calculator

An atom's identity — its element, charge, and structure — is entirely determined by the count of its three subatomic particles. Enter the number of protons, neutrons, and electrons into the Atom Calculator to get the Mass Number, atomic charge, element name, and full electron configuration. If protons and electrons don't match, the calculator automatically identifies the result as an ion.

The number of protons defines the element. For carbon, Z = 6.

Neutrons reside in the nucleus alongside protons.

For a neutral atom, electrons equal protons. Fewer or more electrons create ions.

Results

Mass Number (A)

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Atomic Number (Z)

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Atomic Charge (Ion Charge)

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Neutrons (N = A − Z)

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Element

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Electron Configuration

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Frequently Asked Questions

What is an atom?

An atom is the smallest unit of matter that retains the chemical properties of an element. It consists of a central nucleus containing protons and neutrons, surrounded by a cloud of electrons. Protons and neutrons are collectively called nucleons.

What are atoms made of?

Atoms are made of three subatomic particles: positively-charged protons and electrically neutral neutrons (both in the nucleus), and negatively-charged electrons that orbit the nucleus. The number of protons determines which element the atom belongs to.

How do I calculate the atomic number?

The atomic number (Z) equals the number of protons in the nucleus. For example, carbon has 6 protons, so its atomic number is 6. The atomic number uniquely identifies an element on the periodic table.

How do I find the mass number of an atom?

The mass number (A) is the total count of protons and neutrons in the nucleus: A = protons + neutrons. For a carbon-12 atom with 6 protons and 6 neutrons, the mass number is 12. Electrons are not included because their mass is negligible.

What is the mass number of an atom of helium that contains 2 neutrons?

Helium always has 2 protons (Z = 2). With 2 neutrons, the mass number A = 2 + 2 = 4. This is the most common isotope, helium-4.

Which elementary particle gives an atom its identity?

Protons give an atom its identity. The number of protons — the atomic number — determines which element an atom is. Changing the proton count transforms it into a different element entirely.

What is the atomic number for 6 protons, 7 neutrons, and 6 electrons?

The atomic number equals the number of protons, so Z = 6. This is carbon. With 7 neutrons, the mass number is 13, making it carbon-13, a stable isotope of carbon. Because electrons equal protons, the atom is electrically neutral.

How is atomic charge (ion charge) calculated?

Atomic charge = protons − electrons. A neutral atom has equal protons and electrons (charge = 0). If an atom loses electrons, it becomes a positively charged cation. If it gains electrons, it becomes a negatively charged anion.