Which Element Has the Lowest Melting Point?

The element with the lowest melting point is helium — and it’s such an extreme case that it breaks the usual idea of a melting point. At normal atmospheric pressure, helium never becomes a solid at all, not even at absolute zero. It needs to be squeezed to about 25 times atmospheric pressure before it will freeze, at around 0.95 K (−272.2 °C).

The lowest melting points (from our element data)

Rank	Element	Melting point (K)	Melting point (°C)
1	Helium	0.95 (under pressure)	−272.2
2	Hydrogen	13.81	−259.3
3	Neon	24.56	−248.6
4	Fluorine	53.53	−219.6
5	Oxygen	54.36	−218.8
6	Nitrogen	63.15	−210.0
7	Argon	83.8	−189.4
8	Krypton	115.79	−157.4
9	Xenon	161.36	−111.8
10	Chlorine	171.65	−101.5

Every element on the list is a gas at room temperature, made of small atoms or small molecules held together only by weak London dispersion forces.

Why helium refuses to freeze

Two things conspire against solid helium:

• Extremely weak attractions. Helium atoms have just two electrons in a tight, non-polarizable shell, so the dispersion forces between them are the weakest of any substance.
• Quantum “zero-point” motion. Even at absolute zero, particles can’t be perfectly still — quantum mechanics forbids it. For heavier atoms that residual jiggling is negligible, but helium atoms are so light and so weakly attracted that the zero-point motion alone is enough to keep them from locking into a lattice.

Below about 2.17 K, liquid helium-4 becomes a superfluid: it flows with zero viscosity, creeps up and over the walls of its container, and passes through pores too tiny for any normal liquid. Liquid helium is essential for cooling the superconducting magnets in MRI scanners.

The lowest-melting metals

Metal	Melting point (°C)
Mercury	−38.8
Francium	~27 (estimated)
Cesium	28.4
Gallium	29.8
Rubidium	39.3
Potassium	63.4
Sodium	97.8

Mercury is the only metal that’s liquid at room temperature. Cesium and gallium melt just above it — a warm summer day would do it, and gallium famously melts in your hand (body temperature is about 37 °C). Gallium is safe to handle, unlike cesium, which would react with the moisture on your skin. See liquid elements at room temperature.

Why do these metals melt so easily? The alkali metals have only one valence electron each and large atoms, so their metallic bonding is weak. Mercury’s low melting point is a more exotic story involving relativistic effects on its tightly held 6s electrons.

Lowest-melting nonmetal solid

Among elements that are solid at room temperature and aren’t metals, white phosphorus melts at just 44 °C, which is part of why it’s so dangerous — it can ignite spontaneously in air.

Quick answers

What element has the lowest boiling point? Also helium, at 4.22 K (−268.9 °C) — the lowest of any substance.

What’s the lowest melting point of any metal? Mercury, at −38.8 °C.

Does anything melt lower than helium? Its lighter isotope, helium-3, also stays liquid down to absolute zero at normal pressure, and needs about 29 atmospheres to freeze.

See the trend

The melting point trend map shows the low-melting gases on the right, the soft alkali metals on the left, and the refractory metals blazing in the middle. For the other extreme, see the element with the highest melting point.