Science: Nuclear Physics and Radioactivity Worksheet

Question 1

Define the term isotope and explain how isotopes of the same element are different from one another.

Accepted Answer

An isotope is an atom of the same element that has the same number of protons but a different number of neutrons. Isotopes of the same element have the same atomic number but different mass numbers.

Question 2

Carbon-14 has 6 protons and 8 neutrons. Write its mass number and explain what the number means.

Accepted Answer

The mass number of carbon-14 is 14. The mass number is the total number of protons and neutrons in the nucleus, so 6 plus 8 equals 14.

Question 3

Compare alpha, beta, and gamma radiation by describing what each one is and how penetrating it is.

Accepted Answer

Alpha radiation consists of helium nuclei with 2 protons and 2 neutrons and has low penetrating power. Beta radiation consists of fast-moving particles such as electrons or positrons and has medium penetrating power. Gamma radiation is high-energy electromagnetic radiation and has the greatest penetrating power of the three.

Question 4

During alpha decay, what happens to the atomic number and mass number of the nucleus?

Accepted Answer

During alpha decay, the atomic number decreases by 2 and the mass number decreases by 4. This happens because the nucleus emits an alpha particle containing 2 protons and 2 neutrons.

Question 5

A radioactive sample has a half-life of 10 years. If the sample starts with 80 grams, how much will remain after 30 years?

Accepted Answer

After 30 years, 10 grams will remain. Three half-lives pass in 30 years, so the amount changes from 80 grams to 40 grams, then to 20 grams, and then to 10 grams.

Question 6

Explain why radioactive decay is considered a random process for a single nucleus but predictable for a large sample.

Accepted Answer

Radioactive decay is random for a single nucleus because it is impossible to know exactly when that nucleus will decay. For a large sample, the overall pattern becomes predictable because many atoms decay according to a stable statistical rate described by the half-life.

Question 7

If a radioisotope has a half-life of 6 hours, what fraction of the original sample remains after 18 hours? Also state the percent remaining.

Accepted Answer

After 18 hours, 1/8 of the original sample remains, which is 12.5 percent. This is because 18 hours is three half-lives, and the sample is halved three times.

Question 8

Describe one medical use of radioactivity and explain why it is useful in that application.

Accepted Answer

One medical use of radioactivity is cancer treatment with radiation therapy. It is useful because carefully targeted radiation can damage or destroy cancer cells while doctors work to limit harm to nearby healthy tissue.

Question 9

State the law of conservation of charge and mass number as it applies to nuclear equations.

Accepted Answer

In a nuclear equation, the total mass number must be the same on both sides of the equation, and the total atomic number or charge must also be the same on both sides. This allows missing particles or nuclei to be identified by balancing the equation.

Question 10

A nucleus emits beta-minus radiation. Describe what happens inside the nucleus during this process.

Accepted Answer

During beta-minus decay, a neutron in the nucleus changes into a proton and emits an electron. As a result, the atomic number increases by 1 while the mass number stays the same.

Question 11

List two safety practices used when working with radioactive materials and explain how each one reduces exposure.

Accepted Answer

One safety practice is limiting the time spent near the source, which reduces the total radiation dose received. Another safety practice is using shielding such as lead or concrete, which blocks or reduces the amount of radiation that reaches the body.

Question 12

A sample begins with 1600 undecayed nuclei. After 4 half-lives, how many undecayed nuclei remain?

Accepted Answer

After 4 half-lives, 100 undecayed nuclei remain. The sample is halved four times: 1600, 800, 400, 200, and 100.

Science: Nuclear Physics and Radioactivity

Science: Nuclear Physics and Radioactivity

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