How atomic weights change with scientific understanding
By 
Kit Chapman2025-07-28T08:53:00
Why do the atomic weights on the periodic table keep changing? Kit Chapman meets the team behind the decimal places
It’s easy to think the periodic table never changes. It’s found on the wall of every lab and science classroom in the world. It’s a guide to the building blocks of matter, and they aren’t known to change over time. But nothing could be further from the truth. The periodic table is the ultimate living document of chemistry – and its updates happen more often than even most chemists realise.