A mole is a measurement of a ‘batch’ of particles. It is easier to describe the number of moles of a substance rather than the number of atoms as atoms are very small. Relative atomic mass is the ...

Thank you for bringing to my attention the recent International Union of Pure & Applied Chemistry report “Atomic weights of the elements 2009” (C&EN, Dec. 20 ...

For the first time those little numbers that appear beneath some of the commonest elements in the periodic table boxes are about to change from a single value to an interval of numbers An ...

The most precise measurement to date of the proton-electron mass ratio suggests that the proton may be lighter than previously thought. The result, from researchers in the Netherlands and France, ...