Question 1

Which of the following statements best describes isotopes?

Accepted Answer

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

Question 2

A sample of carbon contains both $$^{12}\mathrm{C}$$ and $$^{14}\mathrm{C}. $$Which of the following is true about these two isotopes?

Accepted Answer

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

Question 3

Which of the following best distinguishes mass number from average atomic mass?

Accepted Answer

Mass number is always a whole number, while average atomic mass is usually not.

Question 4

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

Accepted Answer

Using $$^{14}\mathrm{C} to $$determine the age of ancient artifacts.

Question 5

A student is given a sample of calcium carbonate ($$\mathrm{CaCO}_3) $$and heats it to produce calcium oxide ($$\mathrm{CaO}) $$and carbon dioxide ($$\mathrm{CO}_2). $$Which type of chemical reaction is this?

Accepted Answer

Decomposition reaction

Question 6

Which of the following best describes a compound?

Accepted Answer

A substance formed when two or more different elements chemically combine.

Question 7

According to Bohr’s model, what happens when an electron absorbs energy?

Accepted Answer

It moves to a higher energy shell.

Question 8

Which of the following is true about the energy released when an electron moves from a higher to a lower shell in Bohr’s model?

Accepted Answer

The energy is released as a photon, which may be visible as light.

Question 9

Which equation correctly represents the law of universal gravitation as given in the study materials?

Accepted Answer

$$F = \frac{G m_1$ m_2$}{r^2$}$$

Question 10

A fossil is analyzed and found to have half the amount of $$^{14}\mathrm{C}$$ compared to a living organism. What can be inferred about the age of the fossil?

Accepted Answer

It is approximately one half-life of $$^{14}\mathrm{C}$$ old.

Question 11

Which of the following best explains why average atomic mass is not a whole number?

Accepted Answer

It is a weighted average of all naturally occurring isotopes of an element.

Question 12

Which of the following statements about photons is correct according to Bohr’s model?

Accepted Answer

Photons are emitted when electrons move to a lower energy shell.

Question 13

A patient is treated for thyroid cancer using $$^{131}\mathrm{I}. $$What property of $$^{131}\mathrm{I}$$ makes it suitable for this treatment?

Accepted Answer

It is a radioactive isotope that can target thyroid tissue.

Question 14

Which of the following best describes the relationship between an element and a compound?

Accepted Answer

A compound consists of two or more different elements chemically combined.

Question 15

If an atom has 17 protons and 18 neutrons, what is its mass number?

Accepted Answer

$$35$$

Question 16

Which of the following is a correct statement about electron arrangement in Bohr’s model?

Accepted Answer

Electrons occupy specific shells around the nucleus.

Question 17

A student analyzes the decomposition of $$\mathrm{CaCO}_3$$ and finds that the mass of $$\mathrm{CaO}$$ produced is less than the original mass of $$\mathrm{CaCO}_3. $$What accounts for the missing mass?

Accepted Answer

The mass is accounted for by the $$\mathrm{CO}_2$$ gas released.

Question 18

Which of the following equations correctly represents the distance fallen by an object under gravity after time $$t$$?

Accepted Answer

$$d = \frac{1}{2} g t^2$

Question 19

Which of the following best explains why the arrangement of electrons in shells is important?

Accepted Answer

It determines the types of bonds an atom can form.

Question 20

Which of the following is a correct comparison between $$\mathrm{U}-235 $$and $$\mathrm{C}-14$$?

Accepted Answer

$$\mathrm{U}-235 is $$used in nuclear reactors, while $$\mathrm{C}-14 is $$used in dating ancient objects.

Atomic Structure, Isotopes, and Electron Arrangement

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