---
title: "Meitnerium (Mt): Atomic Mass, Electron Configuration & Properties"
url: https://www.moldraw.com/elements/meitnerium.html
description: "Meitnerium (Mt), element 109: atomic mass [278], electron configuration *[Rn] 5f¹⁴ 6d⁷ 7s², group 9, period 7, d-block unknown (probably transition metal). Melting and boiling point, density, electronegativity and shells."
lang: en
publisher: Scidart Academy
generated: 2026-11-03
---
109Mt[278]

# Meitnerium (Mt) – element 109

Meitnerium is a chemical element with the symbol **Mt** and atomic number **109**. It is a unknown (probably transition metal) in group 9, period 7 of the periodic table (d-block), and is a solid at room temperature.

Meitnerium (Mt) has atomic number 109, atomic mass [278] and electron configuration *[Rn] 5f14 6d7 7s2.

[Download periodic table PDF](https://www.moldraw.com/printables/periodic-table.pdf)[Open interactive periodic table](https://www.moldraw.com/tools/free-chem-tools/interactive-periodic-table.html)

## Meitnerium facts

| Symbol | Mt |
| --- | --- |
| Atomic number | 109 |
| Atomic mass | [278] |
| Category | unknown (probably transition metal) |
| Group | group 9 |
| Period | 7 |
| Block | d-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d7 |
| Noble-gas notation | *[Rn] 5f14 6d7 7s2 |
| Electrons per shell | 2, 8, 18, 32, 32, 15, 2 |

## Bohr model and shells

Meitnerium has 109 electrons in 7 shells: 2, 8, 18, 32, 32, 15, 2. Full configuration and noble-gas notation are in the table; work out any element or ion with the [electron configuration calculator](https://www.moldraw.com/tools/free-chem-tools/electron-configuration-calculator.html).

## Physical and atomic properties

| Density | 37.4 g/cm³ |
| --- | --- |
| Discovered by | Gesellschaft für Schwerionenforschung |

Use the atomic mass in the [molar mass calculator](https://www.moldraw.com/tools/free-chem-tools/molar-mass-calculator.html) for any formula containing Mt.

## Position in the periodic table

Tap any element to open its page.

## Frequently asked questions

### What is the atomic mass of meitnerium?

The atomic mass of meitnerium is [278] (mass number of its longest-lived isotope, since it has no stable isotope).

### What is the electron configuration of meitnerium?

Meitnerium has 109 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d⁷, or *[Rn] 5f¹⁴ 6d⁷ 7s² in noble-gas notation. Electrons per shell: 2, 8, 18, 32, 32, 15, 2.

### Is meitnerium a metal?

Yes. Meitnerium is a unknown (probably transition metal).

### Where is meitnerium on the periodic table?

Meitnerium is in group 9, period 7, in the d-block.

Data: [Periodic-Table-JSON](https://github.com/Bowserinator/Periodic-Table-JSON) (CC BY-SA 3.0); standard atomic weights from IUPAC (abridged). Values in brackets are the mass number of the longest-lived isotope.