Revised table of atoms proposed

By Dr David Whitehouse
BBC News Online science editor

Katharina Lodders points the way

The Periodic Table of the elements has been rewritten by a US scientist.

Dr Katharina Lodders, of Washington University has devised a system that represents the abundance of elements found within our Solar System.

She says that scientists studying the birth of the Sun and planets find the new table more useful than the old.

It is forcing a revision of the amount and role of ice in the formation of rocky and icy moons in our own planetary system's cold outer reaches.

Quick reference

In 1869, Russian chemist Dimitry Ivanovich Mendeleyev produced the Periodic Table of the Elements - a chart that reflected their properties.

It became a touchstone for generations of chemists and helped scientists determine the reasons for the curious regularities seen in element properties. It opened the door to a new way to study atomic structure.

Now, Katharina Lodders of Washington University has produced a new periodic table that is slanted towards astronomers.

The revised Periodic Table will be of more use in the study of the formation of the planets

More details

She calls it the Cosmochemical Periodic Table of the Elements in our Solar System.

"This table reflects the work of many astronomers going back to the 60s and 70s," she says.

Instead of using the usual ways to categorise atoms, such as weight and melting and boiling points, Dr Lodders has focused on the abundances of the atoms in space and the temperatures at which the elements condense.

Her periodic table is also colour-coded to indicate the usual state of the elements.

"The idea was to combine everything for easy comparison and quick reference," she says.

The new table should prove valuable for researchers studying the planets and their moons, as well as meteorites and asteroids.

Icy moons

In the past, astronomers assumed that the elements on the Sun's surface represented the average makeup of the planets, but they now know this is not the case.

Dr Lodders' table takes that into account. "It turns out that these abundances are only roughly half of that previously thought," she says.

This is important because if the amount of carbon and oxygen in the Sun and Solar System is revised downwards, then our understanding of the formation of planets and moons will have to be reassessed.

She added: "It means less oxygen is available to form ices, which is an important factor in understanding the chemistry of the outer Solar System - giant planets, their satellites and other icy bodies such as comets."

Her work is to be published in a forthcoming issue of the Astrophysical Journal.