Mendeleev
Periodic table · chemistry · physics
Element story

Helium

Atomic number 2 means that every Helium nucleus contains 2 protons. That proton count is the element's identity: change it and you no longer have Helium.

Start with the nucleus

Atomic number 2 means that every Helium nucleus contains 2 protons. That proton count is the element's identity: change it and you no longer have Helium.

Helium (He) is chemical element 2. It belongs to the noble gases, and its reference state at room temperature is a gas. Those basic facts are a useful starting point for its chemistry and applications.

In practice, it turns up most often in balloons, medical imaging equipment and cryogenics.

See the atom

Conceptual visual: electron shells are a learning aid, not a literal picture of quantum orbitals.

What this number means

Atomic number 2 means that every Helium nucleus contains 2 protons. That proton count is the element's identity: change it and you no longer have Helium.

Keep exploring

→ Helium · Atomic structure · Periodic trends

2HeHelium
Helium · He · Z = 2

Helium (He) is chemical element 2. It belongs to the noble gases, and its reference state at room temperature is a gas. Those basic facts are a useful starting point for its chemistry and applications.

Understanding the element

Helium (He) is chemical element 2. It belongs to the noble gases, and its reference state at room temperature is a gas. Those basic facts are a useful starting point for its chemistry and applications.

Where do we encounter it?

In practice, it turns up most often in balloons, medical imaging equipment and cryogenics.

What its position in the table tells us

Helium sits in period 1, group 18 and the S block. That location is useful because neighbouring elements often share trends in valence electrons, oxidation states and bonding behaviour.