Berkelium

Named for Berkeley, and a rare starting material for making even heavier elements.

At a glance

Symbol: Bk
Atomic number: 97
Mass number of its longest-lived isotope: [247]
Group: none; it sits in the actinide row below the table
Period: 7
Family: actinide
Electron configuration: [Rn] 5f⁹ 7s²
Electronegativity: 1.30
Common ions: Bk³⁺ and Bk⁴⁺
Isotopes: none are stable; ²⁴⁷Bk lasts longest, about 1,400 years

On the table

Period 7, in the actinide row set below the main table. The other actinides are tinted, and every cell opens its own article.

Electrons and bonding

Radioactive, like every actinide. It gives up electrons to form positive ions.

Properties

State at 25 °C: solid
What it looks like: silvery, radioactive metal
Melting point: 1050 °C
Boiling point: not known
Density: 14.8 g/cm³

Where it is found

Not found in nature; made in minute amounts in high-flux reactors such as the one at Oak Ridge, Tennessee.

Discovery and name

Stanley Thompson, Albert Ghiorso and Glenn Seaborg made it in December 1949 at Berkeley by bombarding americium with alpha particles, and named it after the city.

What it is used for

Research only. In 2009, 22 milligrams of berkelium-249 made at Oak Ridge were flown to Russia and bombarded to make tennessine.

In compounds

BkO₂berkelium dioxideBkCl₃berkelium chloride

Handle with care

Radioactive, and only ever available in milligram amounts.