A

Atomic Number

Z = number of protons in nucleus
Quick Reference
Formula / NotationZ = number of protons in nucleus
Also Known AsProton number; nuclear charge (Z); atomic charge; Z number

What is Atomic Number?

The atomic number (symbol: Z) is the number of protons found in the nucleus of an atom of a given element. It uniquely identifies each chemical element — no two elements have the same atomic number. In a neutral atom, the number of protons equals the number of electrons. The atomic number determines an element's position in the periodic table.

Formula & Notation

Z = number of protons in nucleus

Other Names / Synonyms: Proton number; nuclear charge (Z); atomic charge; Z number

Properties & Characteristics

Symbol Z; always a positive integer; equals number of protons; determines element identity; equals electron count in neutral atom; determines chemical properties and position in periodic table; isotopes have same Z but different mass number A; ranges from 1 (hydrogen) to 118 (oganesson)

Uses & Applications

Identifying elements; understanding electron configuration and periodicity; nuclear chemistry and physics; isotope notation (ᴬ_Z X); mass spectrometry interpretation; predicting chemical behaviour of elements

Safety Information

No hazard — a fundamental atomic property.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Atomic Number
Formula Z = number of protons in nucleus
Synonyms Proton number; nuclear charge (Z); atomic charge; Z number

Frequently Asked Questions

The atomic number (symbol: Z) is the number of protons found in the nucleus of an atom of a given element. It uniquely identifies each chemical element — no two elements have the same atomic number. In a neutral atom, the number of protons equals the number of electrons. The atomic number determines an element's position in the periodic table.

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