---
title: "Polonium (Po) — element 84"
description: "Polonium is element 84, symbol Po, most stable isotope 209. Configuration, properties, uses and neighbours."
url: https://atoneplace.net/element/polonium/
site: "At One Place"
---

# Polonium (Po)

**Polonium — element 84: Po**

[209] · Metalloid · period 6, group 16

Polonium-210 puts out about 140 watts of heat per gram from alpha decay alone — a half-gram pellet glows red hot in the dark and will melt itself. Marie Curie found it first, before radium, and named it after Poland, which did not then exist as a country; she was making a political point in a chemistry paper. It became infamous in 2006 when Alexander Litvinenko was killed with a dose in a cup of tea: alpha radiation does not penetrate skin or a teapot, so it is harmless outside the body and catastrophic inside it, which is exactly what makes it a poison rather than a hazard.

## Properties

- **Atomic number:** 84
- **Symbol:** Po
- **Mass number of most stable isotope:** [209]
- **Category:** Metalloid
- **Group:** 16
- **Period:** 6
- **Block:** p-block
- **Electron configuration:** [Xe] 6s² 4f¹⁴ 5d¹⁰ 6p⁴
- **Electrons per shell:** 2, 8, 18, 32, 18, 6
- **Melting point:** 527 K — 253.9 °C — 488.9 °F
- **Boiling point:** 1,235 K — 961.9 °C — 1763.3 °F
- **Density:** 9.32 g/cm³
- **Electronegativity:** 2 (Pauling)
- **Oxidation states:** +4, +2
- **Discovered:** 1898 by Marie and Pierre Curie

## Electron configuration

- **Full:** 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁴
- **Noble gas shorthand:** [Xe] 6s² 4f¹⁴ 5d¹⁰ 6p⁴
- **Shells:** K: 2 · L: 8 · M: 18 · N: 32 · O: 18 · P: 6

## What it is used for

- Antistatic brushes for cleaning camera lenses and film
- Heat sources for early space probes, including Lunokhod
- Neutron initiators in early nuclear weapon designs

## Hazards

- Around 250 billion times more toxic by mass than hydrogen cyanide when ingested
- Emits alpha particles that are stopped by paper but devastating internally
- Volatile enough to spread as contamination at room temperature

> No stable isotope; the mass given is the mass number of polonium-209, the longest-lived at about 124 years. Filed as a metalloid following the CRC and PubChem classification, though its bulk properties are those of a metal and several periodic tables call it a post-transition metal.

## Neighbours in the table

| Z | Element | Symbol | Mass |
| --- | --- | --- | --- |
| 82 | Lead | Pb | 207.2 |
| 83 | Bismuth | Bi | 208.98 |
| 84 | Polonium ← | Po | [209] |
| 85 | Astatine | At | [210] |
| 86 | Radon | Rn | [222] |

## Group 16

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Polonium sits in group 16 with oxygen, sulfur, selenium, tellurium, livermorium.

## Common questions

### What is the atomic number of polonium?

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

### What is the symbol for polonium?

Po.

### What is the electron configuration of polonium?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁴, or [Xe] 6s² 4f¹⁴ 5d¹⁰ 6p⁴ in noble-gas shorthand.

### What is the melting point of polonium?

527 K — 253.9 °C — 488.9 °F

## Related pages

- [Lead (Pb)](https://atoneplace.net/element/lead/)
- [Bismuth (Bi)](https://atoneplace.net/element/bismuth/)
- [Astatine (At)](https://atoneplace.net/element/astatine/)
- [Radon (Rn)](https://atoneplace.net/element/radon/)
- [Oxygen (O)](https://atoneplace.net/element/oxygen/)
- [Sulfur (S)](https://atoneplace.net/element/sulfur/)
- [Selenium (Se)](https://atoneplace.net/element/selenium/)
- [Tellurium (Te)](https://atoneplace.net/element/tellurium/)
- [Livermorium (Lv)](https://atoneplace.net/element/livermorium/)

## Sources

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