Scientists Unlock Secrets of H-bomb Element Einsteinium

Einsteinium occupies atomic No. 99 on the periodic table in the company of other very heavy and radioactive elements like californium and berkelium. Some radioactive elements, notably uranium, exist in meaningful quantities in Earth's crust (at 2.8 parts per million, there's more uranium underground than gold). But even heavier elements, including einsteinium, can only be created artificially by exploding a hydrogen bomb or by slamming subatomic particles together in a reactor.

What makes an element radioactive? In the case of einsteinium and its neighbors at the bottom of the periodic table, it's the sheer size of their atoms, explains Joseph Glajch, a pharmaceutical chemist who has worked extensively with other radioactive elements used for medical imaging.

"When elements get to be a certain size the nucleus of the atom becomes so large that it disintegrates," says Glajch. "What happens is that it spits out neutrons and/or protons and electrons and decays down to a lower elemental state."

As radioactive elements decay, they cast off clusters of subatomic particles that take the form of alpha particles, beta particles, gamma rays and other radiation. Some types of radiation are relatively harmless, while others can inflict damage on human cells and DNA.

As radioactive elements decay, they also form different isotopes that have different atomic weights. An element's atomic weight is calculated by adding the number of neutrons in the nucleus to the number of protons. For example, the einsteinium collected in the South Pacific in 1952 was an isotope called einsteinium-253, which has 99 protons and 154 neutrons.

But isotopes don't last forever. They each have a different "half-life," which is the estimated time for half of the material to decay into a new isotope or a lower element altogether. Einsteinium-253 has a half-life of just 20.5 days. Uranium-238, on the other hand, which is the most common isotope of uranium found in nature, has a half-life of 4.46 billion years.

One of the hard things about synthesizing heavy radioactive elements like einsteinium in the lab (and by lab, we mean highly specialized nuclear reactors) is that large elements start to decay very quickly.

"As you create bigger and bigger elements and isotopes, it gets more and more difficult to keep them around long enough to see them," says Glajch.

That's why there was so much excitement recently in the chemistry world when a team of scientists successfully held on to a sample of short-lived einsteinium long enough to measure some of the chemical properties of this ultra-rare element.

The scientists, led by Rebecca Arbergel of the Lawrence Berkeley National Laboratory, waited patiently for a tiny sample of einsteinium-254 produced by the Oak Ridge National Laboratory in Tennessee. The sample weighed in at 250 nanograms or 250 billionths of a gram and had a half-life of 276 days. When the COVID-19 pandemic hit in 2020, the research was sidelined for months, during which 7 percent of the sample degraded every 30 days.

Abergel's breakthrough came with the creation of a molecular "claw" that could hold a single atom of einsteinium-254 in place long enough to measure things like the length of its molecular bonds and at what wavelength it emits light. Both of these measurements are critical to understanding how einsteinium and its heavy cousins could potentially be used for things like cancer treatment.