Berkelium (Bk)

Berkelium's one practical use is as a target: 22 milligrams of berkelium-249, made over two years at Oak Ridge, was shipped to Dubna in Russia and bombarded with calcium-48 to create element 117, tennessine. The timing was tight, because berkelium-249 has a 330-day half-life, so the target was decaying while the experiment ran. Only about a gram of berkelium has ever been made in total, and the entire world stock at any moment is a few tens of milligrams.

Properties

Atomic number

97

Symbol

Bk

Mass number of most stable isotope

[247]

Category

Actinide

Period

7

Block

f-block

Electron configuration

[Rn] 7s² 5f⁹

Electrons per shell

2, 8, 18, 32, 27, 8, 2

Melting point

1,323 K — 1049.8 °C — 1921.7 °F

Density

14 g/cm³

Electronegativity

1.3 (Pauling)

Oxidation states

+3, +4

Discovered

1949 by Stanley Thompson, Albert Ghiorso and Glenn Seaborg

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f⁹

Noble gas shorthand

[Rn] 7s² 5f⁹

Shells

K: 2 · L: 8 · M: 18 · N: 32 · O: 27 · P: 8 · Q: 2

What it is used for

• The target material used to make tennessine, element 117

Hazards

• Intensely radioactive; accumulates in bone

No stable isotope; the mass given is the mass number of berkelium-247, the longest-lived at 1,380 years. The boiling point is omitted — no measurement exists, only extrapolations. Named after Berkeley, California, one of a cluster of place-named elements from the same laboratory.

Neighbours in the table