---
title: "Hydrogen (H) — element 1"
description: "Hydrogen is element 1, symbol H, atomic weight 1.008. Configuration, properties, uses and neighbours."
url: https://atoneplace.net/element/hydrogen/
site: "At One Place"
---

# Hydrogen (H)

**Hydrogen — element 1: H**

1.008 u · Nonmetal · period 1, group 1

A hydrogen atom is one proton and one electron, which makes it the only element whose exact quantum mechanics can be solved on paper. It is about 90% of all atoms in the universe by count, but only about 0.14% of the Earth's crust by mass, because the young Earth was too warm and too small to hold on to it. Almost all the hydrogen you will ever meet is locked into water or hydrocarbons rather than floating free.

## Properties

- **Atomic number:** 1
- **Symbol:** H
- **Standard atomic weight:** 1.008 u
- **Category:** Nonmetal
- **Group:** 1
- **Period:** 1
- **Block:** s-block
- **Electron configuration:** 1s¹
- **Electrons per shell:** 1
- **Melting point:** 13.81 K — -259.3 °C — -434.8 °F
- **Boiling point:** 20.28 K — -252.9 °C — -423.2 °F
- **Density:** 0.00008988 g/cm³
- **Electronegativity:** 2.2 (Pauling)
- **Oxidation states:** +1, -1
- **Discovered:** 1766 by Henry Cavendish

## Electron configuration

- **Full:** 1s¹
- **Noble gas shorthand:** 1s¹
- **Shells:** K: 1

## What it is used for

- Ammonia synthesis for fertiliser — by far the largest single use
- Removing sulfur from crude oil in refinery hydrotreaters
- Turning liquid vegetable oils into solid fats
- Fuel-cell buses, trains and forklifts
- Coolant inside large power-station generators

## Hazards

- Flammable in air across an unusually wide range, roughly 4% to 75% by volume
- Burns with a flame that is nearly invisible in daylight
- Colourless and odourless, so leaks are not detectable by smell

> IUPAC publishes an interval, [1.00784, 1.00811], because the deuterium fraction varies between natural waters; 1.008 is the conventional value. The density given is the gas at 0 °C and 101.325 kPa.

## Neighbours in the table

| Z | Element | Symbol | Mass |
| --- | --- | --- | --- |
| 1 | Hydrogen ← | H | 1.008 |
| 2 | Helium | He | 4.0026 |
| 3 | Lithium | Li | 6.94 |

## Group 1

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Hydrogen sits in group 1 with lithium, sodium, potassium, rubidium, cesium, francium.

## Common questions

### What is the atomic number of hydrogen?

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

### What is the symbol for hydrogen?

H.

### What is the electron configuration of hydrogen?

1s¹, or 1s¹ in noble-gas shorthand.

### What is the melting point of hydrogen?

13.81 K — -259.3 °C — -434.8 °F

## Related pages

- [Helium (He)](https://atoneplace.net/element/helium/)
- [Lithium (Li)](https://atoneplace.net/element/lithium/)
- [Lithium (Li)](https://atoneplace.net/element/lithium/)
- [Sodium (Na)](https://atoneplace.net/element/sodium/)
- [Potassium (K)](https://atoneplace.net/element/potassium/)
- [Rubidium (Rb)](https://atoneplace.net/element/rubidium/)
- [Cesium (Cs)](https://atoneplace.net/element/cesium/)
- [Francium (Fr)](https://atoneplace.net/element/francium/)

## Sources

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