Magnetism and magnetic fields Study Guide

Atoms are the fundamental building blocks of matter, composed of a central nucleus surrounded by electrons. The nucleus contains protons and neutrons. Changes within these atomic structures can lead to the emission or absorption of radiation, spanning a wide range of frequencies across the electromagnetic spectrum.

One common way radiation is generated is through changes in the energy levels of electrons within an atom. When an electron moves from a higher energy level to a lower one, it emits a photon of electromagnetic radiation. The energy of this photon, and thus its frequency, corresponds to the energy difference between the levels. Conversely, an atom can absorb a photon if its energy matches the difference needed to excite an electron to a higher energy level. These processes are responsible for characteristic emission and absorption spectra of elements, often seen in the visible and ultraviolet parts of the spectrum.

Changes within the nucleus of an atom also generate radiation. This occurs during radioactive decay, where unstable atomic nuclei transform into more stable forms by emitting particles and/or energy. Alpha decay involves the emission of an alpha particle (a helium nucleus), beta decay involves the emission of a beta particle (an electron or positron), and gamma decay involves the emission of gamma rays, which are high-energy electromagnetic waves. These nuclear changes typically produce radiation with very high frequencies and energies, such as gamma rays and X-rays, far beyond those produced by electron transitions. Understanding these processes is crucial for applications such as medical imaging, nuclear power, and dating archaeological artefacts.

Some atomic nuclei are inherently unstable. This instability arises from an imbalance in the number of protons and neutrons within the nucleus. To achieve a more stable configuration, these unstable nuclei undergo a process called radioactive decay. During radioactive decay, the unstable nucleus spontaneously transforms, emitting particles or energy in the process. The types of emissions are categorised into three main groups: alpha particles, beta particles, and gamma rays. Sometimes, neutrons are also emitted during certain decay processes. An alpha particle consists of two protons and two neutrons, essentially a helium nucleus. A beta particle is a high-energy electron emitted from the nucleus when a neutron converts into a proton. Gamma rays are high-energy electromagnetic radiation, similar to X-rays but with shorter wavelengths, and are often emitted after alpha or beta decay when the nucleus is left in an excited state. These emissions carry energy away from the nucleus, leading to a more stable atomic structure.