---
title: "Mercury (Hg) — element 80"
description: "Mercury is element 80, symbol Hg, atomic weight 200.59. Configuration, properties, uses and neighbours."
url: https://atoneplace.net/element/mercury/
site: "At One Place"
---

# Mercury (Hg)

**Mercury — element 80: Hg**

200.59 u · Transition metal · period 6, group 12

Mercury is liquid at room temperature for the same relativistic reason gold is yellow: its 6s electrons are held so tightly and so close that mercury atoms barely bond to one another, giving it a melting point of −38.8 °C where cadmium above it melts at 321 °C. A blood pressure of "120 over 80" is still quoted in millimetres of mercury, as is the pressure in a vacuum system, because a mercury column was the instrument for three centuries. The Mad Hatter is not a joke: hat makers used mercury nitrate to felt fur and developed tremors, irritability and slurred speech from breathing the fumes.

## Properties

- **Atomic number:** 80
- **Symbol:** Hg
- **Standard atomic weight:** 200.59 u
- **Category:** Transition metal
- **Group:** 12
- **Period:** 6
- **Block:** d-block
- **Electron configuration:** [Xe] 6s² 4f¹⁴ 5d¹⁰
- **Electrons per shell:** 2, 8, 18, 32, 18, 2
- **Melting point:** 234.32 K — -38.8 °C — -37.9 °F
- **Boiling point:** 629.88 K — 356.7 °C — 674.1 °F
- **Density:** 13.5336 g/cm³
- **Electronegativity:** 2 (Pauling)
- **Oxidation states:** +2, +1
- **Discovered:** Known since antiquity

## Electron configuration

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

## What it is used for

- Fluorescent and compact fluorescent lamps
- Mercury vapour in some UV sterilising lamps
- Dental amalgam fillings
- Electrical switches, relays and tilt sensors, now mostly replaced
- Historically, thermometers, barometers and blood pressure cuffs

## Hazards

- Mercury vapour from a spill is odourless and causes cumulative nervous system damage
- Methylmercury builds up through the food chain and crosses the placenta
- Spilled droplets lodge in floor cracks and evaporate for years

> Filed as a transition metal because it is in the d-block; under IUPAC's strict definition group 12 does not qualify. Mercury is the only metal that is liquid at room temperature — bromine is liquid too, but is not a metal.

## Neighbours in the table

| Z | Element | Symbol | Mass |
| --- | --- | --- | --- |
| 78 | Platinum | Pt | 195.08 |
| 79 | Gold | Au | 196.97 |
| 80 | Mercury ← | Hg | 200.59 |
| 81 | Thallium | Tl | 204.38 |
| 82 | Lead | Pb | 207.2 |

## Group 12

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Mercury sits in group 12 with zinc, cadmium, copernicium.

## Common questions

### What is the atomic number of mercury?

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

### What is the symbol for mercury?

Hg.

### What is the electron configuration of mercury?

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

### What is the melting point of mercury?

234.32 K — -38.8 °C — -37.9 °F

## Related pages

- [Platinum (Pt)](https://atoneplace.net/element/platinum/)
- [Gold (Au)](https://atoneplace.net/element/gold/)
- [Thallium (Tl)](https://atoneplace.net/element/thallium/)
- [Lead (Pb)](https://atoneplace.net/element/lead/)
- [Zinc (Zn)](https://atoneplace.net/element/zinc/)
- [Cadmium (Cd)](https://atoneplace.net/element/cadmium/)
- [Copernicium (Cn)](https://atoneplace.net/element/copernicium/)

## Sources

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