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LITHOEN

Chemical element

Calcium

A major element of plagioclase feldspar, pyroxene and carbonate minerals, and the element whose partitioning drives much of the compositional variation in igneous rocks.

Classification

atomic number
20
symbol
Ca
block
s

How this record is known

3
Settled consensus
Cited as the accepted position of the discipline.

3 of 3 claims on this page cite at least one registered source. Counts describe how each statement is known, not how likely it is to be true.

What Lithoen records

Each claim states how it is known and cites its evidence.

Established20 protons

Calcium has atomic number 20: its nucleus contains 20 protons, and that is what makes it calcium.

  • definition basis: Atomic number is definitional: an atom with a different proton count is a different element, whatever else it shares.

Evidence support: Supported by the cited evidence one source

Evidence: Commission on Isotopic Abundances and Atomic Weights (IUPAC) 2024 Primary authority

Established40.078 u

The standard atomic weight of calcium is 40.078(4), a single value because its isotopic composition does not vary appreciably between normal materials.

  • definition basis: CIAAW Standard Atomic Weights 2024; the parenthesised digits are the uncertainty in the last figures as published.
  • precision note: A property of the element as found in normal materials, not the mass of any individual atom.

Evidence support: Supported by the cited evidence one source

Evidence: Commission on Isotopic Abundances and Atomic Weights (IUPAC) 2024 Primary authority

In the knowledge graph

  • Calcium essential constituent of Anorthite
  • Calcium essential constituent of Calcite
  • Calcium essential constituent of Diopside
  • Calcium essential constituent of Dolomite
  • Calcium essential constituent of Grossular

Record last updated 2026-09-06. Corrections follow the published corrections policy; superseded claims are retained, never silently edited.