Question 1

Which of the following best defines an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 2

A nucleus of chlorine contains 17 protons and 20 neutrons. What is its nuclear symbol?

Accepted Answer

$$\mathrm{^{37}_{17}Cl}$$

Question 3

Which factor most directly determines the stability of an atom?

Accepted Answer

The ratio of protons to neutrons in the nucleus.

Question 4

If a nucleus of uranium has a mass number of 238, how many neutrons does it contain?

Accepted Answer

146

Question 5

Which of the following statements about radioactive decay is correct?

Accepted Answer

Radioactive decay changes the number of protons or neutrons in a nucleus.

Question 6

What is the definition of half-life?

Accepted Answer

The time required for half the atoms in a radioactive sample to decay.

Question 7

A 2.00 gram sample of radium-226 has a half-life of 1600 years. How much will remain after three half-lives?

Accepted Answer

0.25 grams

Question 8

Which type of radiation requires the heaviest shielding for protection?

Accepted Answer

Gamma radiation

Question 9

When a beta particle ($$\beta^-) is $$released from an unstable nucleus, what change occurs?

Accepted Answer

A neutron is converted into a proton.

Question 10

Which of the following is a real-world application of isotopes in medicine?

Accepted Answer

Using iodine-131 to treat thyroid disorders.

Question 11

Which equation correctly represents alpha decay of uranium-238?

Accepted Answer

$$\mathrm{^{238}_{92}U \$$rightarrow ^{234}$$_{90}Th $$+ ^{4}$$_{2}He}$$

Question 12

After 24 days, how much of a 100 g sample of a radioactive isotope with a half-life of 8 days remains?

Accepted Answer

12.5 g

Question 13

Which of the following best describes the risk associated with alpha radiation?

Accepted Answer

It is dangerous if inhaled or ingested but is stopped by skin or paper.

Question 14

Which symbol represents a beta particle?

Accepted Answer

$$\mathrm{^{0}_{-1}e}$$

Question 15

Which of the following changes occurs in the nucleus when a positron ($$\beta^+) is $$emitted?

Accepted Answer

A proton is converted into a neutron.

Question 16

Which type of nuclear emission does NOT change the atomic number or mass number of the nucleus?

Accepted Answer

Gamma emission

Question 17

Which of the following is a correct statement about the use of isotopes in carbon dating?

Accepted Answer

Carbon dating measures the ratio of $$^{14}C to$$ $$^{12}C in a $$sample to estimate its age.

Question 18

Which of the following is a danger associated with exposure to gamma radiation?

Accepted Answer

It can cause mutations in DNA leading to cancer.

Question 19

Which of the following best explains why nuclear power plants use uranium-235?

Accepted Answer

Uranium-235 can undergo fission, releasing large amounts of energy.

Question 20

Which of the following is a correct description of beta decay?

Accepted Answer

A neutron in the nucleus is converted into a proton and an electron is emitted.

Isotopes, Nuclear Chemistry, and Radioactivity: Study Guide

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