Use this chemistry calculator to reproduce a named relationship with explicit quantities and units for study, laboratory planning, or an independent numerical check.

Ion

Ion formula including charge, such as Na+, Mg2+, or Cl-.

Look up a Shannon effective ionic radius for a common six-coordinate ion; ionic radius depends on oxidation state and coordination number. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Ionic radius (pm)

Effective ionic radius for coordination number 6.

• The result is conditional on the stated model, constants, standard state, temperature, pressure, composition, and unit basis. Real mixtures and measurements can depart from ideal behavior and carry uncertainty not represented by a single calculated value.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Check units and significant figures, compare the result with limiting cases, and use measured or source-specific constants where available. Laboratory, safety, and regulatory decisions require validated methods and appropriate uncertainty analysis.

• Coordination Number Calculator

  Look up the number of nearest neighbours around an atom for the common cubic and close-packed structures.

• Madelung Constant Lookup

  Look up the electrostatic Madelung constant for common ionic crystal structures.

• VSEPR Geometry Lookup

  Look up the VSEPR molecular geometry from the number of bonded atoms and lone pairs on a central atom.