---
title: "Meitnerium (Mt) — element 109"
description: "Meitnerium is element 109, symbol Mt, most stable isotope 278. Configuration, properties, uses and neighbours."
url: https://atoneplace.net/element/meitnerium/
site: "At One Place"
---

# Meitnerium (Mt)

**Meitnerium — element 109: Mt**

[278] · Transition metal · period 7, group 9

Meitnerium honours Lise Meitner, who worked out that the uranium nucleus had split when Otto Hahn found barium in his samples and could not explain it — and who was left off the Nobel Prize he received for it. It is the only element named solely for a non-mythological woman; curium honours Marie and Pierre Curie together. The discovery was a single atom, produced at Darmstadt in August 1982 and identified by its decay chain, and only a few dozen atoms have been made since.

## Properties

- **Atomic number:** 109
- **Symbol:** Mt
- **Mass number of most stable isotope:** [278]
- **Category:** Transition metal
- **Group:** 9
- **Period:** 7
- **Block:** d-block
- **Electron configuration:** [Rn] 7s² 5f¹⁴ 6d⁷
- **Electrons per shell:** 2, 8, 18, 32, 32, 15, 2
- **Oxidation states:** +9, +8, +6, +4, +3, +1
- **Discovered:** 1982 by Peter Armbruster, Gottfried Münzenberg and colleagues at GSI Darmstadt

## Electron configuration

- **Full:** 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d⁷
- **Noble gas shorthand:** [Rn] 7s² 5f¹⁴ 6d⁷
- **Shells:** K: 2 · L: 8 · M: 18 · N: 32 · O: 32 · P: 15 · Q: 2

## What it is used for

- Research only; no application outside the laboratory

## Hazards

- Intensely radioactive; exists only as individual atoms in an accelerator

> Melting point, boiling point, density and electronegativity are omitted: no measurement is possible. The electron configuration is calculated, not observed. The mass given is the mass number of meitnerium-278, the longest-lived at a few seconds.

> Several physical properties are not listed for meitnerium because no bulk sample has ever existed. Only a handful of atoms have been produced, often with half-lives measured in seconds, so published melting points and densities for elements in this range are calculations rather than measurements. They are omitted rather than presented as observed values.

## Neighbours in the table

| Z | Element | Symbol | Mass |
| --- | --- | --- | --- |
| 107 | Bohrium | Bh | [270] |
| 108 | Hassium | Hs | [269] |
| 109 | Meitnerium ← | Mt | [278] |
| 110 | Darmstadtium | Ds | [281] |
| 111 | Roentgenium | Rg | [282] |

## Group 9

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Meitnerium sits in group 9 with cobalt, rhodium, iridium.

## Common questions

### What is the atomic number of meitnerium?

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

### What is the symbol for meitnerium?

Mt.

### What is the electron configuration of meitnerium?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d⁷, or [Rn] 7s² 5f¹⁴ 6d⁷ in noble-gas shorthand.

## Related pages

- [Bohrium (Bh)](https://atoneplace.net/element/bohrium/)
- [Hassium (Hs)](https://atoneplace.net/element/hassium/)
- [Darmstadtium (Ds)](https://atoneplace.net/element/darmstadtium/)
- [Roentgenium (Rg)](https://atoneplace.net/element/roentgenium/)
- [Cobalt (Co)](https://atoneplace.net/element/cobalt/)
- [Rhodium (Rh)](https://atoneplace.net/element/rhodium/)
- [Iridium (Ir)](https://atoneplace.net/element/iridium/)

## Sources

- Typical range compiled from manufacturer specifications — At One Place (/about/)