Welcome to this deck on atomic structure and radioactivity. We'll start by looking inside the atom at the protons, neutrons, and electrons. Then, we'll explore how our model of the atom has changed over time. Finally, we will cover the topic of radioactivity, including the different types of radiation, the concept of half-life, and how to stay safe when working with radioactive materials.

At the centre of every atom is a tiny, dense nucleus. This nucleus contains two types of particles: protons and neutrons. Orbiting the nucleus in paths called shells, or energy levels, are much smaller particles called electrons. Protons have a positive charge, neutrons have no charge, and electrons have a negative charge. Because the number of positive protons is equal to the number of negative electrons, an atom has no overall charge.

To compare the particles, scientists use relative charges and masses. A proton has a relative charge of plus one. An electron has a relative charge of minus one. A neutron is neutral, so its relative charge is zero.