2.21. Atomic Structure: Radioactive Decay

2.21. Atomic Structure: Radioactive Decay

Radioactive decay is one of the most fascinating aspects of chemistry, which combines nuclear physics with chemistry to create a bridge between these two disciplines. It is a natural phenomenon that occurs when an unstable atom loses energy, emitting radiation. This process is fundamental to understanding the atomic structure and its behavior, being a crucial part of the chemistry curriculum for the ENEM test.

What is radioactive decay?

Radioactive decay is a process that occurs when an unstable atom transforms into an atom of another element, emitting radiation in the process. Unstable atoms that undergo radioactive decay are known as radioisotopes or radionuclides. The instability of atoms is usually caused by an excess of neutrons or protons in the atomic nucleus, which leads to the emission of particles to reach a more stable state.

Types of Radioactive Decay

There are three main types of radioactive decay: alpha (α), beta (β) and gamma (γ). In alpha decay, the atomic nucleus emits an alpha particle, which is composed of two protons and two neutrons. This results in a new element with an atomic number two units smaller and an atomic mass four units smaller.

In beta decay, a neutron in the atomic nucleus is transformed into a proton, with the emission of a beta particle (a high-energy electron). This results in a new element with an atomic number one unit higher, but the atomic mass remains the same.

In gamma decay, the atomic nucleus emits energy in the form of gamma radiation, but there is no change in atomic number or atomic mass. Gamma radiation is a form of electromagnetic radiation, similar to visible light but of higher energy.

Radioactive Decay and the Half-Life

Half-life is a crucial concept in radioactive decay. It is the time required for half of the atoms in a radioactive sample to decay. Each radioisotope has a specific half-life, which is a measure of its instability. For example, uranium-238 has a half-life of 4.5 billion years, which means it takes 4.5 billion years for half of a sample of uranium-238 to decay.

Applications of Radioactive Decay

Radioactive decay has many practical applications. It is used in radiometric dating to determine the age of rocks and fossils. In medicine, radioisotopes are used in diagnoses and treatments, such as radiation therapy for cancer. In power generation, nuclear fission of radioisotopes is the basis of nuclear power.

Conclusion

Understanding radioactive decay is essential for understanding atomic structure and for applying chemistry in everything from archeology to medicine. By mastering this topic, you will be well prepared to answer questions related to atomic structure in the ENEM test.

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