Isotopes of Hydrogen Model

Quick Answer: The Isotopes of Hydrogen Model is a chemistry and physics display comparing the three isotopes of hydrogen side by side: protium with no neutrons, deuterium with one and tritium with two. Each has one proton and one electron, so students can see that isotopes share an atomic number but differ in mass number.

Three Atoms, One Element

The listing image of the isotopes of hydrogen model shows three atoms on one panel, each with a single electron in orbit and a nucleus that grows from one particle to three. Placing them side by side makes the definition of an isotope visible: the proton count, and therefore the element, stays the same, while the neutron count changes the mass.

Protium, hydrogen-1, is by far the most common form. Deuterium, hydrogen-2, is stable and occurs naturally in small amounts; water made with it, called heavy water, is denser than ordinary water and is used as a moderator in some nuclear reactors. Tritium, hydrogen-3, is radioactive, decaying by beta emission with a half-life of about 12.3 years, and is used in self-luminous signs and as a fuel in fusion research.

Because all three isotopes have one electron, they share the same chemistry: all form H₂ molecules and react with oxygen to form water. Their differences are physical, in mass, density and nuclear stability. The model is a good lead-in to relative atomic mass, since the value for hydrogen reflects the natural mix of isotopes, and to nuclear notation, in which the three are written ¹H, ²H and ³H.

Specifications

Applications

• Defining isotopes, atomic number and mass number
• Introducing nuclear notation and relative atomic mass
• Discussing heavy water, radioactivity and half-life
• Preparing students for the deuterium-tritium fusion reaction

Care & Handling

• Clean the panel with a soft, slightly damp cloth and dry it straight away.
• Keep the model away from heat and direct sunlight.
• Store it upright in a cupboard so the nucleus beads are not pressed.

Why Choose LabEquip

Physics and chemistry teachers usually buy this model for the atomic structure chapter, where isotopes are first defined. LabEquip lists it in the STEM kits range, and schools covering nuclear energy often add the Nuclear Fusion Educational Model, in which deuterium and tritium fuse. Send your order details through the contact page.

Frequently Asked Questions

What are isotopes?

Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons. They have the same atomic number and chemistry but different mass numbers.

Why do the hydrogen isotopes have the same chemical properties?

Chemical behaviour depends on electrons, and all three isotopes have one proton and one electron. Only their masses differ, which causes small differences in reaction rates but not in the kind of reactions they undergo.

What is heavy water?

Heavy water is water in which the hydrogen atoms are deuterium. It is roughly ten percent denser than ordinary water and is used as a moderator in some nuclear reactors because it slows neutrons without absorbing many of them.

Is tritium radioactive?

Yes. Tritium has an unstable nucleus with two neutrons and decays by emitting a beta particle, turning into helium-3. Its half-life is about 12.3 years.

Which hydrogen isotope is most common?

Protium, with no neutrons, makes up almost all natural hydrogen. Deuterium is present as a small fraction, and tritium occurs only in tiny traces, produced mainly by cosmic rays in the upper atmosphere.

Why are deuterium and tritium important in fusion?

They fuse more readily than ordinary hydrogen. When a deuterium nucleus and a tritium nucleus join, they form helium-4 and a neutron and release a large amount of energy, the reaction most fusion research is based on.

Last Updated: September 2026