Helium is a light, very unreactive gas.
Uses and research
It fills some balloons and its extremely cold liquid is used to cool equipment.
A family that reacts reluctantly
The noble gases occupy the right-hand column. The familiar members react reluctantly, but this does not mean that compounds are impossible: some heavier noble gases form compounds. Membership of a group is a clue, not a guarantee of every property. Oganesson has not been observed as an ordinary bulk gas.
What the atomic number tells us
Helium has atomic number 2. This is the number of protons in its nucleus. A neutral atom also has 2 electrons. Losing or gaining electrons makes an ion; it does not change the element unless the proton count changes.
The model's rings help count electrons by shell. They are not actual circular paths. A model of one atom and the properties of a whole material are different levels of description.
Temperature and state
25°C: Gas
Illustrative particle motion: sizes, distances and speeds are not to scale. Particles represent atoms or molecules.
← CoolHeat →
Boiling point -268.93°C
Helium does not become solid at 1 atmosphere.
Pure element at 1 atmosphere. Image conditions are explained in captions. Pictures do not change with temperature.