Q: A sample of carbon-14 ($$^{14}\mathrm{C}) is $$used in radiocarbon dating. If the half-life of carbon-14 is 5730 years, how old is a fossil that contains $$\frac{1}{32} of $$its original carbon-14?

$$5 \text{ half-lives} \times 5730 \text{ years} = 28,650 \text{ years}$$

Q: A 24 mg sample of technetium-99m ($$^{99m}\mathrm{Tc}) is $$used in a medical scan. If the half-life is 6 hours, how much remains after 18 hours?

$$24 \times (\frac{1}{2})^3$ = 3 \text{ mg}$$

Q: A hospital patient is to receive a 3 mCi dose of gallium-67. If the available solution contains 12 mCi/mL, how many milliliters should be administered?

$$\frac{3 \text{ mCi}}{12 \text{ mCi/mL}} = 0.25 \text{ mL}$$

Question 1

Which of the following statements best describes the location and relative mass of subatomic particles in an atom?

Accepted Answer

Protons and neutrons are found in the nucleus and have nearly equal mass, while electrons are found in the electron cloud and have negligible mass.

Question 2

An atom of sodium has an atomic number of 11 and a mass number of 23. How many neutrons does it contain?

Accepted Answer

$$23 - 11 = 12$$ neutrons

Question 3

Which of the following best defines an isotope?

Accepted Answer

Atoms of the same element with the same number of protons but different numbers of neutrons.

Question 4

A sample of carbon-14 ($$^{14}\mathrm{C}) is $$used in radiocarbon dating. If the half-life of carbon-14 is 5730 years, how old is a fossil that contains $$\frac{1}{32} of $$its original carbon-14?

Accepted Answer

$$5 	ext{ half-lives} 	imes 5730 	ext{ years} = 28,650 	ext{ years}$$

Question 5

Which type of nuclear radiation has the greatest penetrating power and requires thick lead or concrete for shielding?

Accepted Answer

Gamma ($$\gamma) $$rays

Question 6

What is the balanced nuclear equation for the alpha decay of uranium-238 ($$^{238}_{92}\mathrm{U}$$)?

Accepted Answer

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

Question 7

A 24 mg sample of technetium-99m ($$^{99m}\mathrm{Tc}) is $$used in a medical scan. If the half-life is 6 hours, how much remains after 18 hours?

Accepted Answer

$$24 	imes (\frac{1}{2})^3$ = 3 	ext{ mg}$$

Question 8

Which of the following statements about the biological effects of radiation is correct?

Accepted Answer

Ionizing radiation can remove electrons from atoms, making them more reactive and potentially damaging living cells.

Question 9

Which of the following is the correct symbolic notation for an atom with 17 protons, 18 neutrons, and 17 electrons?

Accepted Answer

$$^{35}_{17}\mathrm{Cl}$$

Question 10

A hospital patient is to receive a 3 mCi dose of gallium-67. If the available solution contains 12 mCi/mL, how many milliliters should be administered?

Accepted Answer

$$\frac{3 	ext{ mCi}}{12 	ext{ mCi/mL}} = 0.25 	ext{ mL}$$

Question 11

Which of the following best explains why radioisotopes with short half-lives are preferred for diagnostic imaging in medicine?

Accepted Answer

They minimize the patient's exposure to radiation by decaying quickly.

Question 12

Which of the following nuclear equations represents the beta decay of manganese-56 ($$^{56}_{25}\mathrm{Mn}$$)?

Accepted Answer

$$^{56}_{25}\mathrm{Mn} \$$rightarrow ^{56}$$_{26}\mathrm{Fe} $$+ ^{0}$$_{-1}\mathrm{e}$$

Question 13

Which of the following is a correct statement about the difference between atomic mass and mass number?

Accepted Answer

Mass number is the total number of protons and neutrons in a specific atom, while atomic mass is the weighted average of all naturally occurring isotopes of an element.

Question 14

Which of the following forms of radiation is most likely to be stopped by a sheet of paper and is dangerous only if ingested or inhaled?

Accepted Answer

Alpha ($$\alpha) $$particles

Question 15

A PET scan uses fluorine-18, which decays by positron emission. What happens when the emitted positron encounters an electron in the body?

Accepted Answer

They annihilate each other, producing gamma rays that are detected by the scanner.

Question 16

Which of the following is the correct relationship between the curie (Ci) and the becquerel (Bq)?

Accepted Answer

$$1 	ext{ Ci} = 3.7 	imes 10$$^{10}$$ 	ext{ Bq}$$

Question 17

Which of the following best describes why rapidly dividing cancer cells are more susceptible to ionizing radiation?

Accepted Answer

Their genetic material is exposed more often during cell division, making them more likely to be damaged by radiation.

Question 18

A radioactive isotope has a half-life of 10 days. If you start with 80 mg, how much remains after 30 days?

Accepted Answer

$$80 	imes (\frac{1}{2})^3$ = 10 	ext{ mg}$$

Atoms and Radioactivity: Structure, Isotopes, and Nuclear Chemistry

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