Chapter 20: Problem 5

What is an alpha particle? What happens to the mass number and atomic number of a nuclide that emits an alpha particle?

Short Answer

Expert verified

An alpha particle is a helium nucleus consisting of 2 protons and 2 neutrons. After a nuclide emits an alpha particle, its mass number decreases by 4 and its atomic number decreases by 2, resulting in a new element.

Step by step solution

Define an Alpha Particle

An alpha particle is a type of ionizing radiation composed of 2 protons and 2 neutrons. This is the same as a helium nucleus, and it is denoted by the symbol (α) or sometimes by the symbol He when represented in a nuclear equation.

Understand the changes in mass number and atomic number after alpha decay

When a nuclide emits an alpha particle, its mass number (total number of protons and neutrons in the nucleus) decreases by 4 and its atomic number (number of protons) decreases by 2. This is because the emitted alpha particle contains 2 protons and 2 neutrons.

Identify the New Nuclide

After the emission of an alpha particle, the original nuclide transforms into a new nuclide with different properties (a different element). The new element has an atomic number that is 2 less than the original nuclide and a mass number that is 4 less.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Alpha Decay

Alpha decay is a nuclear process in which an unstable atomic nucleus emits an alpha particle to become more stable. An alpha particle, comprised of 2 protons and 2 neutrons, is essentially a helium-4 nucleus and represents a significant loss from the original nucleus in both mass and charge.

Due to alpha decay, an element can transform into another element positioned two places to the left on the periodic table. This process occurs in the heavy nuclei of certain radioactive elements, such as uranium and radium. The emissions of alpha particles are a natural part of radioactive decay processes.

Mass Number

The mass number of an atom is the total count of protons and neutrons in the nucleus. It provides insight into the total mass of the nucleus since protons and neutrons are substantially heavier than electrons. When alpha decay occurs, the nucleus forfeits 2 protons and 2 neutrons that comprise the emitted alpha particle. Consequently, the mass number of the remaining nuclide is reduced by 4. This reduction is significant as it alters both the physical and chemical properties of the original atom.

Atomic Number

The atomic number indicates the number of protons within an atomic nucleus and essentially defines the chemical element. Following alpha decay, the atomic number decreases by 2, due to the loss of the 2 protons carried away by the alpha particle. This decrease typically changes the type of element, leading to a transformation to a different element with a lower atomic number. For instance, radium (Ra) undergoes alpha decay to form radon (Rn).

Ionizing Radiation

Ionizing radiation is radiation with enough energy to strip electrons from atoms or molecules, thereby ionizing them. Alpha particles are a prime example of ionizing radiation and can cause significant biological damage when they interact with living tissue. Despite their limited ability to penetrate materials, once inside the body, for instance, through inhalation, they can affect biological cells due to their mass and charge. Protecting against ionizing radiation is crucial for both environmental and human health.

Nuclear Equation

A nuclear equation represents the changes undergone by a nuclide during nuclear reactions such as alpha decay. It details the initial nuclide, the emitted alpha particle, and the resultant nuclide. In the case of alpha decay, the nuclear equation will show a decrease in mass number by 4 and a decrease in atomic number by 2. These equations allow scientists and students alike to track the transformation of elements and predict the outcome of radioactive decay processes.

Nuclide Transformation

When a nuclide undergoes alpha decay, it undergoes a nuclide transformation, changing its identity to become a completely different element. This is more than just a loss of particles; it is a fundamental change in the nuclide's properties. In nature and in nuclear reactors, such transformations lead to the creation of different isotopes and elements, contributing to the natural decay series and influencing the synthesis of new materials with various applications in medicine, industry, and research.

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What is an alpha particle? What happens to the mass number and atomic number of a nuclide that emits an alpha particle?

Short Answer

Step by step solution

Define an Alpha Particle

Understand the changes in mass number and atomic number after alpha decay

Identify the New Nuclide

Key Concepts

Alpha Decay

Mass Number

Atomic Number

Ionizing Radiation

Nuclear Equation

Nuclide Transformation

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