---
title: "Promethium (Pm): Atomic Mass, Electron Configuration & Properties"
url: https://www.moldraw.com/elements/promethium.html
description: "Promethium (Pm), element 61: atomic mass [145], electron configuration [Xe] 4f⁵ 6s², group 3, period 6, f-block lanthanide. Melting and boiling point, density, electronegativity and shells."
lang: en
publisher: Scidart Academy
generated: 2026-11-03
---
61Pm[145]

# Promethium (Pm) – element 61

Promethium is a chemical element with the symbol **Pm** and atomic number **61**. It is a lanthanide in group 3 (lanthanides), period 6 of the periodic table (f-block), and is a solid at room temperature.

Promethium (Pm) has atomic number 61, atomic mass [145] and electron configuration [Xe] 4f5 6s2.

[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)

## Promethium facts

| Symbol | Pm |
| --- | --- |
| Atomic number | 61 |
| Atomic mass | [145] |
| Category | lanthanide |
| Group | group 3 (lanthanides) |
| Period | 6 |
| Block | f-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f5 |
| Noble-gas notation | [Xe] 4f5 6s2 |
| Electrons per shell | 2, 8, 18, 23, 8, 2 |

## Bohr model and shells

Promethium has 61 electrons in 6 shells: 2, 8, 18, 23, 8, 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

| Melting point | 1315 K (1041.8 °C) |
| --- | --- |
| Boiling point | 3273 K (2999.8 °C) |
| Density | 7.26 g/cm³ |
| Electronegativity (Pauling) | 1.13 |
| Electron affinity | 12.45 kJ/mol |
| Ionization energies | 540, 1050, 2150 kJ/mol (1st, 2nd, 3rd) |
| Discovered by | Chien Shiung Wu |

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 Pm.

## Position in the periodic table

Tap any element to open its page.

## Frequently asked questions

### What is the atomic mass of promethium?

The atomic mass of promethium is [145] (mass number of its longest-lived isotope, since it has no stable isotope).

### What is the electron configuration of promethium?

Promethium has 61 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f⁵, or [Xe] 4f⁵ 6s² in noble-gas notation. Electrons per shell: 2, 8, 18, 23, 8, 2.

### Is promethium a metal?

Yes. Promethium is a lanthanide.

### Where is promethium on the periodic table?

Promethium is in group 3 (lanthanides), period 6, in the f-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.