Atomic Number Calculator

Every chemical element has a unique atomic number — the count of protons in its nucleus — which defines what that element actually is. Use the Atomic Number Calculator to look up any element by element name, symbol, or atomic number to retrieve its full profile. You'll get the element's atomic number, symbol, name, atomic mass, and its group and period position on the periodic table.

Enter the element name (e.g. Hydrogen), symbol (e.g. H), or atomic number (e.g. 1)

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Atomic Number

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Element Symbol

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Element Name

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Atomic Mass

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Group

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Period

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Frequently Asked Questions

What is an atomic number?

The atomic number is the number of protons in the nucleus of an atom. It determines the identity of an element and its position in the periodic table. Each element has a unique atomic number.

How do you find the atomic number of an element?

You can find the atomic number by looking up the element name or symbol in the periodic table. The atomic number is typically displayed above or below the element symbol and represents the number of protons in the atom's nucleus.

What is the difference between atomic number and atomic mass?

Atomic number is the number of protons in an atom's nucleus, while atomic mass is the average mass of all isotopes of an element, measured in atomic mass units (u). Atomic number determines the element's identity, while atomic mass accounts for both protons and neutrons.

Can two different elements have the same atomic number?

No, two different elements cannot have the same atomic number. The atomic number uniquely identifies each element. If two atoms have the same atomic number, they are the same element, even if they have different numbers of neutrons (isotopes).

What element has the highest atomic number?

Currently, Oganesson (Og) has the highest atomic number at 118. However, scientists continue to discover and synthesize new superheavy elements, so this may change as new elements are confirmed.

How is atomic number related to the number of electrons?

In a neutral atom, the atomic number equals the number of electrons. Since atoms are electrically neutral, the number of positively charged protons must equal the number of negatively charged electrons.

What determines an element's position in the periodic table?

An element's position in the periodic table is determined by its atomic number. Elements are arranged in order of increasing atomic number from left to right and top to bottom. The atomic number also determines the element's chemical properties.

Can the atomic number of an element change?

No, the atomic number of an element cannot change under normal circumstances. If the number of protons in an atom's nucleus changes, it becomes a different element entirely. This only occurs in nuclear reactions or radioactive decay.