Question 1

Which of the following statements correctly describes the location and charge of subatomic particles in an atom?

Accepted Answer

Protons and neutrons are located in the nucleus; electrons are negatively charged and found outside the nucleus.

Question 2

An atom of magnesium has an atomic number of 12 and a mass number of 25. How many neutrons does this atom have?

Accepted Answer

$$25 - 12 = 13$$ neutrons

Question 3

Which of the following best defines an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 4

Given the symbolic notation $$^{37}_{17}\mathrm{Cl}$$, how many electrons does a neutral atom of this isotope have?

Accepted Answer

$$17$$ electrons

Question 5

Which of the following statements correctly distinguishes between mass number and atomic mass?

Accepted Answer

Mass number is the total number of protons and neutrons in one atom; atomic mass is the weighted average of all isotopes.

Question 6

Which type of ionizing radiation has the greatest penetrating power?

Accepted Answer

Gamma ($$\gamma) $$rays

Question 7

A patient receives a dose of $$800$$ mrem of radiation during a medical procedure. If the annual safe exposure limit is $$500$$ mrem, is this dose considered harmful?

Accepted Answer

Yes, because $$800$$ mrem exceeds the annual safe exposure limit.

Question 8

Which of the following is a balanced nuclear equation for the alpha decay of uranium-238?

Accepted Answer

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

Question 9

A radioactive isotope has a half-life of $$3$$ days. If you start with $$80 mg$$, how much remains after $$9$$ days?

Accepted Answer

$$10 mg$$

Question 10

Which unit is used to measure the biological effect of radiation on tissue?

Accepted Answer

Rem (or mrem)

Question 11

Which of the following radioisotopes is commonly used in the diagnosis of thyroid disorders?

Accepted Answer

$$^{131}\mathrm{I}$$

Question 12

Which of the following statements best describes positron emission?

Accepted Answer

A proton is converted into a neutron and a positron is emitted.

Question 13

A sample of $$^{99m}\mathrm{Tc} is $$used in a medical scan. If its half-life is $$6$$ hours, how much of a $$32 mg $$sample remains after $$18$$ hours?

Accepted Answer

$$4 mg$$

Question 14

Which of the following best explains why gamma rays are more dangerous than alpha particles for internal exposure?

Accepted Answer

Gamma rays have higher penetrating power and can damage internal tissues more extensively.

Question 15

Which of the following is the correct symbolic notation for an atom with $$20$$ protons and $$22$$ neutrons?

Accepted Answer

$$^{42}_{20}\mathrm{Ca}$$

Question 16

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 17

Which of the following nuclear equations represents beta decay?

Accepted Answer

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

Question 18

A hospital receives a shipment of $$100$$ mCi of a radioisotope with a half-life of $$8$$ days. How much activity remains after $$24$$ days?

Accepted Answer

$$12.5$$ mCi

Question 19

Which of the following best describes the use of $$^{60}\mathrm{Co} in $$medicine?

Accepted Answer

It is used for the treatment of cancer through external beam radiation therapy.

Question 20

If the atomic mass of chlorine is $$35.45$$ amu, which isotope is most abundant?

Accepted Answer

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

Atoms, Isotopes, and Radioactivity: Structure, Properties, and Applications

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