Chemistry was �brought into the SI� in 1971 when the mole was adopted as the seventh base unit of the SI.  The mole is the unit for Amount of Substance, a base measurable physical quantity.The current definition in use for the mole includes the following:1.  The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is 'mol'.2.  When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.  14th CGPM (1971, Resolution 3)Since 2006, the metrology community has endeavored to redefine the seven base units in terms of explicit constants and this has included the mole.  The new proposed definition of the mole is:The mole, symbol mol, is the SI unit of amount of substance of a specified elementary entity, which may be an atom, molecule, ion, electron, any other particle, or a specified group of such particles; its magnitude is set by fixing the numerical value of the Avogadro constant to be equal to exactly 6.022 141 29 �1023 when it is expressed in the SI unit mol-1.  Topics to be addressed in this presentation include:The mole in use todayA short recent history of the moleDo we need the mole?Brief overview of proposed redefinitions of SI base units in terms of explicit constantsThe new proposed definition of the molePotential consequences from use of the new definition of the mole? This presentation will include an overview of the April 9, 2014 CIPM Consultative Committee for Amount of Substance:  metrology in chemistry (CCQM) Workshop on the redefinition and realization of the mole.

The mole: Its history, definition, redefinition, and realization

248th National Meeting (2014)

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