Radioactive decay - waves and particles Study Guide

The nucleus is the central part of an atom. It is incredibly small in comparison to the overall atom but contains almost all of the atom's mass. The nucleus is primarily composed of two types of subatomic particles: protons and neutrons. Protons are positively charged particles, each carrying a charge of +1 elementary charge. Neutrons, as their name suggests, are neutral particles, meaning they have no electrical charge. Both protons and neutrons are collectively referred to as nucleons. The number of protons in an atom's nucleus is called the atomic number (Z), and this number uniquely identifies an element. For example, all atoms of carbon have 6 protons. Because protons are positively charged, and neutrons are neutral, the entire nucleus of an atom carries a net positive charge. This positive charge is a characteristic property of each specific element. The magnitude of this positive charge depends directly on the number of protons present in the nucleus. A nucleus with more protons will have a greater positive charge. This positive charge is fundamental to how atoms interact with each other and how they form chemical bonds.

Every element on the periodic table is defined by the number of protons in its atoms, which is called the atomic number. For example, all carbon atoms have 6 protons. However, atoms of the same element do not always have the same mass. This variation occurs because atoms of the same element can have different numbers of neutrons in their nucleus. These variations are known as isotopes.

The nucleus of an atom contains protons and neutrons, collectively called nucleons. Protons carry a positive charge, while neutrons have no charge. Both contribute significantly to the atom's mass. The mass number (or nuclear mass) of an atom is the total number of protons and neutrons in its nucleus. If the number of protons defines the element, then a change in the number of neutrons will change the mass number but not the element itself.

Consider hydrogen. The most common isotope, protium, has one proton and no neutrons (mass number 1). Deuterium, another isotope of hydrogen, has one proton and one neutron (mass number 2). Tritium, yet another isotope, has one proton and two neutrons (mass number 3). All three are hydrogen because they all have one proton, but their nuclear masses differ. Isotopes behave chemically in very similar ways because their electron configurations are identical, which is primarily determined by the number of protons. However, their different masses can lead to slight differences in physical properties and nuclear stability. Many isotopes are stable, but some, like Tritium, are unstable and undergo radioactive decay.