Atoms and chemical bonds

How it works

The number of protons (the atomic number Z) decides the element: six protons is always carbon. Neutrons change the mass and stability of the nucleus, giving isotopes such as carbon-12 and carbon-14. When the number of electrons differs from the number of protons, the result is an ion with an electric charge. Electrons fill shells and subshells according to the electron configuration; chemical behaviour depends mostly on the valence electrons in the outer shell.

mass number A = Z + Ncharge = Z − number of electrons

Try it yourself

1. In “Build an atom”, start with carbon (6 protons, 6 neutrons, 6 electrons). Add two neutrons: you get carbon-14, and the app shows that its nucleus is radioactive.
2. Build sodium (11 protons, 12 neutrons) and remove one electron. You get the cation Na⁺ with a charge of +1. Its single valence electron is in the configuration [Ne] 3s¹.
3. In “Chemical bonds”, compare water H₂O, where atoms share electron pairs, with sodium chloride NaCl, where an electron moves from sodium to chlorine.
4. In “Practice”, build the requested particles, for example the ion O²⁻: 8 protons and 10 electrons.

Model limitations

The atom is a teaching diagram with shells drawn as circles. Real electrons are not little balls on orbits; quantum mechanics describes them with orbitals. Isotope stability comes from a nuclide table, but the model does not explain why a nucleus is stable.

Related experiments

• Electric circuits
• Ideal gas
• Ray optics