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What is Radioactive Decay — Reading Comprehension

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"This comprehensive middle school science passage defines radioactive decay as the process by which unstable atomic nuclei become stable by releasing particles and energy. It details the three main types of decay—alpha, beta, and gamma—explaining the specific changes that occur in the nucleus for each. The passage introduces the concept of half-life as a key measure of decay rate and connects the topic to real-world applications like radiometric dating and medical procedures. This resource is designed to help students understand core concepts in physical science, aligning with NGSS standards related to matter, its structure, and its interactions. It provides a foundational understanding of nuclear processes and their significance."

CONTENT PREVIEW

At the heart of every atom lies a nucleus, a dense center containing protons and neutrons. While most atoms have a stable nucleus that remains unchanged, some have an unstable, or radioactive, nucleus. Radioactive decay is the process by which these unstable nuclei lose energy by emitting particles and radiation to become more stable. This fundamental process is a natural part of the universe, transforming one element into another over time. The rate at which this decay occurs is unique to each radioactive isotope and is measured by its half-life.

There are three primary types of radioactive decay, each distinguished by the particles or energy released. In alpha decay, an unstable nucleus ejects an alpha particle, which is essentially the nucleus of a helium atom (two protons and two neutrons). This results in the original atom transforming into a new element with a lower atomic number. In beta decay, a neutron inside the nucleus converts into a proton and an electron. The electron is then ejected from the nucleus as a beta particle, causing the atom's atomic number to increase by one, and again, creating a different element. Finally, gamma decay involves an unstable nucleus releasing excess energy in the form of high-energy electromagnetic waves called gamma rays. Unlike alpha and beta decay, gamma decay does not change the number of protons or neutrons, so the atom remains the same element.

Radioactive decay has many important real-world applications. For example, the predictable rate of decay, or half-life, of certain isotopes like Carbon-14 is used in radiometric dating to determine the age of ancient artifacts and fossils. This process helps scientists understand Earth's history and the history of life. In medicine, controlled amounts of radioactive isotopes are used for medical imaging, such as PET scans, and for treating cancer. The ability to harness this natural process allows for advancements in science, technology, and healthcare.

Fun Fact: The banana is naturally radioactive due to the presence of a small amount of the isotope potassium-40. This tiny amount is harmless and contributes to the background radiation we are all exposed to every day.

What is the main purpose of radioactive decay for an unstable nucleus?

To gain more neutronsTo become more stableTo increase its sizeTo change its mass

An alpha particle is composed of which two subatomic particles?

Protons and electronsNeutrons and electronsProtons and neutronsElectrons only

What happens to an atom's atomic number during beta decay?

It decreases by oneIt increases by oneIt stays the sameIt doubles

Which type of decay involves the nucleus releasing only energy, without changing its elemental identity?

Alpha decayBeta decayGamma decayBoth alpha and beta decay

If an isotope has a half-life of 10 years, how much of a 100-gram sample will remain after 20 years?

50 grams25 grams10 grams0 grams

According to the passage, what is a key application of radioactive decay's predictable rate?

Powering a nuclear reactorCreating new elementsMedical imagingRadiometric dating

What is the central idea of the passage?

Explaining the dangers of radiation.Describing the components of an atom.Defining and explaining radioactive decay and its uses.Comparing stable and unstable elements.

Why is gamma decay different from alpha and beta decay?

It changes the atomic number.It emits a particle instead of energy.It does not change the atom's element.It has a longer half-life.