Orbit of Atom Model

Quick Answer: The Orbit of Atom Model is a Bohr-style teaching display that shows electrons travelling in circular orbits, or shells, around a central nucleus. Teachers use it to explain energy levels, how many electrons each shell can hold, and why the electrons in the outermost orbit decide how an atom reacts.

Electrons in Fixed Orbits

The listing image of the orbit of atom model shows a nucleus at the centre surrounded by concentric rings of coloured beads, each ring standing for one electron orbit. It is built to show the arrangement of electrons rather than the make-up of the nucleus, so it answers a particular question: where are the electrons, and why are they grouped the way they are?

In 1913 Niels Bohr proposed that electrons move only in certain allowed orbits, each with a fixed energy, and do not radiate energy while they stay in them. An electron can jump to a higher orbit by absorbing exactly the right amount of energy and falls back by emitting it as light, which explains why each element gives a line spectrum rather than a continuous rainbow. Moving outward, the orbits are labelled K, L, M and N, or numbered 1, 2, 3 and 4.

Each shell holds at most 2n² electrons, where n is the shell number, giving 2, 8, 18 and 32. For the first 20 elements the outermost shell holds no more than eight, which is why school arrangements such as 2,8,8,2 for calcium look the way they do. The model is a stepping stone: senior students later learn that electrons occupy orbitals, regions of probability, rather than neat circular paths.

Applications

• Introducing Bohr’s model and energy levels
• Teaching shell capacity and electron arrangements for the first 20 elements
• Explaining line spectra and flame test colours
• Identifying valence electrons and predicting valency

Specifications

Care & Handling

• Keep the model upright and avoid bending the orbit rings.
• Wipe with a soft dry cloth; do not use solvents on the beads or panels.
• Store in a cupboard away from sunlight and damp.

Why Choose LabEquip

Science teachers usually choose this model when introducing Bohr’s theory, before moving on to specific elements. LabEquip lists it in the STEM kits range along with the Structure of Atom Model, which focuses on protons, neutrons and the nucleus. Send your enquiry through the contact page.

Frequently Asked Questions

What did Bohr propose about electron orbits?

Bohr proposed that electrons move around the nucleus only in certain fixed orbits, each with a definite energy. While in an allowed orbit an electron does not lose energy; it absorbs or emits energy only when it jumps between orbits.

How many electrons can each shell hold?

The maximum is 2n squared, where n is the shell number. The first shell holds 2, the second 8, the third 18 and the fourth 32, although for the first 20 elements the outermost shell never holds more than eight.

Why do elements give coloured flames?

Heat excites electrons into higher orbits. When they fall back, they give out light of particular energies, and so of particular colours. Each element has its own set of orbit energies, so each gives its own flame colour and line spectrum.

What are valence electrons?

They are the electrons in the outermost orbit. Their number decides how an atom bonds and reacts, so elements with the same number of valence electrons, like those in one group, behave similarly.

What are the limitations of the Bohr model?

It works well for hydrogen but cannot explain the spectra of atoms with many electrons. Modern quantum theory replaces fixed circular orbits with orbitals, regions where an electron is likely to be found.

How is the orbit model different from the structure of atom model?

The orbit model concentrates on the electron shells and energy levels. The structure of atom model concentrates on the particles in the atom, the protons and neutrons in the nucleus and the electrons outside, and their charges.

Last Updated: September 2026