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 ...

Nineteen elements on the periodic table — including gold, cadmium, arsenic and aluminum — are getting their atomic weights adjusted. The International Union of Pure and Applied Chemistry (IUPAC) ...

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 ...

Standard atomic weights, those numbers emblazoned under the elements on the periodic table, were once thought of as unchanging constants of nature. But researchers have tweaked the atomic weights of ...

Mass spectrometry—a technology that is constantly being made more accurate and reliable—is used every two years to revise the standard atomic weights of select elements. This year, the International ...

Conventional neutron numbers are based on the approximations that the mass of the electron is zero and that those of the proton and neutron are each equal to unity. It was shown, by using the exact ...

Atoms of different elements usually have different mass numbers, but they can be the same. For example, the mass number of argon atoms and calcium atoms can both be 40. The symbol for an atom can be ...