Question 1

Which of the following best defines an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 2

What primarily determines the stability of an atomic nucleus?

Accepted Answer

The ratio of neutrons to protons in the nucleus.

Question 3

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons.

Question 4

What is the nuclear symbol for a chlorine atom with 17 protons and 20 neutrons?

Accepted Answer

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

Question 5

A nucleus of uranium has a mass number of 238. If uranium's atomic number is 92, how many neutrons does it contain?

Accepted Answer

146

Question 6

Which of the following best describes radioactive decay?

Accepted Answer

The spontaneous transformation of an unstable atomic nucleus into a lighter nucleus, accompanied by the emission of radiation.

Question 7

What is the definition of half-life?

Accepted Answer

The time it takes for half of the atoms in a radioactive sample to decay.

Question 8

A 2.00 gram sample of radium-226 (half-life = 1600 years) is left undisturbed. How much of the sample will remain after three half-lives?

Accepted Answer

0.50 grams

Question 9

A 100 g sample of a radioactive isotope has a half-life of 8 days. How much of the sample remains after 24 days?

Accepted Answer

12.5 g

Question 10

Which type of radiation requires the heaviest shielding to protect against exposure?

Accepted Answer

Gamma radiation

Question 11

What happens to the atomic number and mass number of a nucleus when it emits an alpha particle?

Accepted Answer

Atomic number decreases by 2, mass number decreases by 4.

Question 12

Which of the following equations correctly represents beta decay?

Accepted Answer

$$\mathrm{^{14}_{6}C \$$rightarrow ^{14}$$_{7}N $$+ ^{0}$$_{-1}e}$$

Question 13

When a gamma ray is released from an unstable nucleus, what changes occur in the nucleus?

Accepted Answer

No change in atomic number or mass number; the nucleus moves to a lower energy state.

Question 14

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

Accepted Answer

It is dangerous if inhaled or ingested, but cannot penetrate skin.

Question 15

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

Accepted Answer

Using iodine-131 to diagnose and treat thyroid disorders.

Question 16

Which of the following statements about nuclear fission in power plants is correct?

Accepted Answer

Nuclear fission releases energy by splitting heavy nuclei such as uranium-235.

Question 17

What is the main danger of radon gas in homes?

Accepted Answer

It is a radioactive gas that can increase the risk of lung cancer when inhaled.

Question 18

Which of the following best explains how carbon-14 is used in carbon dating?

Accepted Answer

By measuring the amount of carbon-14 remaining in a sample, scientists can estimate the time since the organism died.

Question 19

Which of the following is a correct statement about the emission of a positron from a nucleus?

Accepted Answer

The atomic number decreases by 1.

Question 20

Why is gamma radiation more dangerous than alpha or beta radiation when outside the body?

Accepted Answer

Gamma radiation is highly penetrating and can pass through the body, damaging internal tissues.

Isotopes, Nuclear Chemistry, and Radioactivity: Study Guide

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