CHAPTER 20: RADIOACTIVITY

How do we know the age of ancient artifacts? How can doctors see inside the body without surgery? What is the dangerous glow from nuclear waste? The answer lies in radioactivity—the spontaneous decay of unstable atomic nuclei, accompanied by the emission of radiation. Discovered by Henri Becquerel in 1896, radioactivity has transformed medicine, archaeology, and our understanding of the atom. This chapter will give you mastery over the types of radiation, half-life calculations, nuclear equations, and the crucial balance between the uses and hazards of radioactive materials.

20.1 THE NATURE OF RADIOACTIVITY

20.1.1 Definition

Radioactivity is the spontaneous and random process by which unstable atomic nuclei disintegrate (decay) to form more stable nuclei, emitting radiation in the form of particles or electromagnetic waves.

Key characteristics:

• Spontaneous: Cannot be influenced by external factors like temperature, pressure, or chemical state.
• Random: It is impossible to predict which nucleus will decay next; decay is governed by probability.
• Unstable nuclei: Occurs only in isotopes with an unstable combination of protons and neutrons.

20.1.2 Types of Radiation

There are three main types of nuclear radiation: alpha (α), beta (β), and gamma (γ). They differ in their nature, penetrating power, ionizing ability, and deflection in electric and magnetic fields.

20.2