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Chemistry vocabulary · Atoms and the Periodic Table

Atomic number

Meaning in chemistry, with examples

nounCore term

In chemistry, atomic number means: The number of protons in the nucleus of an atom. It identifies the element: every carbon atom has 6 protons and every oxygen atom has 8.

In Turkish: atom numarası

How it is used

Used with the periodic table, which lists the elements in order of increasing atomic number. Its symbol is Z. Don't mix it up with the mass number (protons plus neutrons), written A.

Example sentences

  1. Iron has an atomic number of 26, so its atoms have 26 protons.

  2. Elements in the periodic table are arranged by increasing atomic number.

Common collocations

  • atomic number of
  • increasing atomic number
  • same atomic number
  • mass number
  • atomThe smallest unit of an element that keeps its chemical identity. It has a tiny nucleus of protons and neutrons, with electrons moving around it.
  • elementA pure substance made of only one kind of atom, all with the same number of protons. It cannot be broken down into simpler substances by chemical reactions.
  • isotopeOne of two or more forms of the same element whose atoms have the same number of protons but a different number of neutrons, such as carbon-12 and carbon-14.
  • periodic tableA chart that arranges all known elements in order of atomic number, in rows called periods and columns called groups. Elements in the same group behave in similar ways.

More terms: Atoms and the Periodic Table

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