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What is an atomic weight?


Atomic weight: mass or weight?
Norman Greenwood Scientist
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 I’ll say one other thing about the Atomic Weights Commission because it has affected teaching to some extent and it is, I think, due to a misconception. Teachers, for very good reason, want to emphasise to their pupils and students that there is a difference between weight and mass. They have different units, they are different physical concepts. Atomic weight is what Dalton called them. You weigh things in a balance... in fact you’re comparing masses. And now, of course, the values that are in the tables are obtained almost exclusively, not chemically, but by mass spectrometry where you actually do, through physical techniques, measure the mass of something.

Norman Greenwood (1925-2012) was born in Australia and graduated from Melbourne University before going to Cambridge. His wide-ranging research in inorganic and structural chemistry made major advances in the chemistry of boron hydrides and other main-group element compounds. He also pioneered the application of Mössbauer spectroscopy to problems in chemistry. He was a prolific writer and inspirational lecturer on chemical and educational themes, and held numerous visiting professorships throughout the world.

Listeners: Brian Johnson

Professor Brian FG Johnson FRS, FRSE, FRS Chem, FAcad Eu, FAS. Professor of Inorganic Chemistry University of Edinburgh 1991-1995, Professor of Inorganic Chemistry University of Cambridge 1995-2005, Master Fitzwilliam College Cambridge 1999-2005. Research interests include studies of transition metal carbonyls, organometallic chemistry, nano- particles and homogeneous catalysis. Professor Johnson is the author of over 1000 research articles and papers.

Tags: Atomic Weights Commission, John Dalton

Duration: 56 seconds

Date story recorded: May 2011

Date story went live: 25 November 2011