Chemistry: Nuclear Chemistry: Fission, Fusion, and Decay Worksheet

Question 1

In alpha decay, uranium-238 becomes thorium-234 and releases an alpha particle. Write the balanced nuclear equation using isotope notation.

Accepted Answer

The balanced nuclear equation is U-238 -> Th-234 + He-4. The mass numbers balance because 238 = 234 + 4, and the atomic numbers balance because 92 = 90 + 2.

Question 2

Carbon-14 undergoes beta-minus decay to form nitrogen-14. Write the balanced nuclear equation and explain what happens to the atomic number.

Accepted Answer

The balanced nuclear equation is C-14 -> N-14 + beta particle. In beta-minus decay, the mass number stays the same and the atomic number increases by 1, changing carbon with atomic number 6 into nitrogen with atomic number 7.

Question 3

A radioactive isotope has a half-life of 8 days. If a sample starts with 80 grams, how many grams remain after 24 days?

Accepted Answer

After 24 days, 10 grams remain. Since 24 days is 3 half-lives, the sample changes from 80 grams to 40 grams to 20 grams to 10 grams.

Question 4

Compare nuclear fission and nuclear fusion in terms of what happens to atomic nuclei.

Accepted Answer

Nuclear fission is the splitting of a large nucleus into smaller nuclei, often releasing neutrons and energy. Nuclear fusion is the combining of small nuclei into a larger nucleus, also releasing energy.

Question 5

Complete and balance this nuclear equation: U-235 + n-1 -> Ba-141 + Kr-92 + ___ n-1.

Accepted Answer

The missing coefficient is 3, so the equation is U-235 + n-1 -> Ba-141 + Kr-92 + 3 n-1. The mass numbers balance because 235 + 1 = 141 + 92 + 3.

Question 6

A nucleus emits a gamma ray. Describe how the mass number and atomic number of the nucleus change.

Accepted Answer

The mass number and atomic number do not change during gamma emission. Gamma radiation is high-energy electromagnetic radiation released when the nucleus loses energy.

Question 7

Radium-226 decays by alpha emission. Identify the daughter isotope by mass number and element name.

Accepted Answer

The daughter isotope is radon-222. Alpha decay lowers the mass number by 4 and the atomic number by 2, so radium-226 with atomic number 88 becomes radon-222 with atomic number 86.

Question 8

A 200 gram sample of iodine-131 decays to 25 grams in 24 days. How many half-lives have passed, and what is the half-life of iodine-131 in this situation?

Accepted Answer

Three half-lives have passed because 200 grams becomes 100 grams, then 50 grams, then 25 grams. The half-life is 8 days because 24 days divided by 3 half-lives equals 8 days per half-life.

Question 9

Explain why a nuclear chain reaction can occur during fission of uranium-235.

Accepted Answer

A nuclear chain reaction can occur because fission of uranium-235 releases neutrons. Those neutrons can strike other uranium-235 nuclei, causing more fission reactions and releasing more neutrons.

Question 10

Hydrogen isotopes can fuse in stars to form helium. Explain why fusion requires extremely high temperature and pressure.

Accepted Answer

Fusion requires extremely high temperature and pressure because positively charged nuclei repel each other. High temperature and pressure give the nuclei enough energy and collisions to get very close and combine.

Question 11

Identify the type of decay represented by this change: P-32 -> S-32 + beta particle.

Accepted Answer

This is beta-minus decay. The mass number stays 32, and the atomic number increases from 15 for phosphorus to 16 for sulfur.

Question 12

A medical tracer has a half-life of 6 hours. A patient receives a dose with an activity of 64 units. How much activity remains after 18 hours?

Accepted Answer

After 18 hours, 8 units of activity remain. Since 18 hours is 3 half-lives, the activity changes from 64 units to 32 units to 16 units to 8 units.

Chemistry: Nuclear Chemistry: Fission, Fusion, and Decay

More Chemistry Worksheets

More Grade 9-12 Worksheets