Hydrogen (H)
Hydrogen is element 1, a reactive nonmetal in period 1, group 1 of the periodic table. At room temperature it is a gas.
Electron configuration 1s1
Electrons per shell 1
Hydrogen data
| Atomic number | 1 |
|---|---|
| Symbol | H |
| Atomic mass | 1.008 u |
| Category | Reactive nonmetal |
| Group | 1 |
| Period | 1 |
| Block | s |
| State at 25 °C | gas |
| Melting point | 14 K (-259.1 °C) |
| Boiling point | 20 K (-253.1 °C) |
| Density | 0.0000899 g/cm³ (0.0899 g/L) |
| Electronegativity (Pauling) | 2.2 |
| Atomic radius | 37 pm |
| 1st ionization energy | 1312 kJ/mol |
| Electron affinity | -73 kJ/mol |
| Oxidation states | -1, +1 |
| Common ion charge | +, − |
| Discovered | 1766 |
Orbital diagram
Each box is one orbital holding up to two electrons of opposite spin. Following Hund’s rule, electrons spread out singly across a subshell before pairing.
Work through hydrogen’s configuration and its ions →
Where hydrogen sits
Hydrogen belongs to the reactive nonmetals. Its Pauling electronegativity of 2.2 is mid-range; see the electronegativity chart and periodic trends for context. To use its mass in a calculation, try the molar mass calculator.
Hydrogen FAQ
What is the electron configuration of hydrogen?
Hydrogen (Z = 1) has the configuration 1s1. In noble-gas shorthand that is 1s1.
How many valence electrons does hydrogen have?
1 (outer shell (n = 1)).
What is the atomic mass of hydrogen?
The standard atomic weight of hydrogen is 1.008 u, so one mole weighs 1.008 g.
Is hydrogen a metal?
No. Hydrogen is a reactive nonmetal.
What is the charge of a hydrogen ion?
Hydrogen most commonly forms H+ or H−.