---
title: "Berkelium (Bk) — element 97"
description: "Berkelium is element 97, symbol Bk, most stable isotope 247. Configuration, properties, uses and neighbours."
url: https://atoneplace.net/element/berkelium/
site: "At One Place"
---

# Berkelium (Bk)

**Berkelium — element 97: Bk**

[247] · Actinide · period 7

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

| Z | Element | Symbol | Mass |
| --- | --- | --- | --- |
| 95 | Americium | Am | [243] |
| 96 | Curium | Cm | [247] |
| 97 | Berkelium ← | Bk | [247] |
| 98 | Californium | Cf | [251] |
| 99 | Einsteinium | Es | [252] |

## Common questions

### What is the atomic number of berkelium?

97. That is the number of protons in its nucleus, which is what defines the element.

### What is the symbol for berkelium?

Bk.

### What is the electron configuration of berkelium?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f⁹, or [Rn] 7s² 5f⁹ in noble-gas shorthand.

### What is the melting point of berkelium?

1,323 K — 1049.8 °C — 1921.7 °F

## Related pages

- [Americium (Am)](https://atoneplace.net/element/americium/)
- [Curium (Cm)](https://atoneplace.net/element/curium/)
- [Californium (Cf)](https://atoneplace.net/element/californium/)
- [Einsteinium (Es)](https://atoneplace.net/element/einsteinium/)

## Sources

- Official vendor product documentation — At One Place (/about/)