Elemental chart updated after 150 years

By Brent Constantin

The periodic table, the bane of every first-year chemistry students’ existence, is facing its first update in 150 years.

Several University of Calgary researchers worked with a team of international scientists to bring forward evidence changing the table of elements.

The research, released in early December, reflects the atomic weight of several elements more accurately than previous charts. The new table will list ten elements– hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine and thallium– as having different atomic weights based on where they are found geographically.

U of C associate professor Michael Wieser, who also serves as secretary of the International Union of Pure and Applied Chemistry’s Commission on Isotopic Abundances and Atomic Weights, said he’s been fascinated with how much attention the story has received.

“I think a lot of that is because even if you didn’t go into science as a career, you still remember that dusty table at the front of the class with all these letters and numbers,” said Wieser.

These charts in textbooks and classrooms will hopefully be updated this year with the new atomic weights, replacing older charts now decades old.

Wieser explained atomic weight is the connection between the mass of the chemical element and the average amount of each isotope present. If researchers want to calculate how much energy might be delivered in a cubic volume of gas or how much protein is in food, they need to know the atomic weight of carbon or nitrogen or other elements.

The original elemental atomic weights were measured decades ago and seen as a constant.

“But we know that the atomic weights for many elements, and the 10 that we’re changing now, do vary in nature,” said Wieser.

Wieser said science has actually known about the changes for some time. Lead, for instance, was found to vary in atomic weight depending on where it was discovered as far back as the 1930s. Despite this, the changes weren’t approved until recently.

The International Union of Pure and Applied Chemistry is the governing body for atomic weights and where publishers get their information from. The next step is to have the updated information added to reference material, something that Wieser is waiting to see.

“It’s going to be very interesting to see how the publishers actually use it, because it is a very different way of presenting these atomic weights,” he said.

The data will impact research depending on the level of accuracy needed in calculations. Researchers looking to be very precise can’t rely on a single value for atomic weight, they’ll have to measure the atomic weight of the particular element sample they’re working with.

“For many people, having an atomic weight to three or four decimal places is sufficient and they don’t need to know it to any better precision than that,” said Wieser. “But some people might need to know very precisely the atomic weight.”

Wieser said one of the goals from updating the data has been to encourage interest from students in the sciences.

“When people are sitting in the classroom, sort of stunned by what the prof is saying and they’re looking into space at the table, maybe they start to wonder why some of these elements have these intervals and that might get people interested to learn more,” said Wieser.