 Revisions in the base set of SI units necessitated redefinitions of the concepts of chemical quantity . Avogadro 's number , and its definition , was deprecated in favor of the Avogadro constant and its definition . Changes in the SI units are proposed to fix the value of the constant to exactly 6.02214X × 1023 when it is expressed in the unit mol − 1 , in which an " X " at the end of a number means one or more final digits yet to be agreed upon . 
