Question 1

Which scientist is credited with the discovery of the law of conservation of mass?

Accepted Answer

Antoine Lavoisier

Question 2

According to Dalton’s atomic theory, which statement is INCORRECT based on modern understanding?

Accepted Answer

Atoms are indestructible and retain their identity in all chemical reactions.

Question 3

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 4

A neutral atom of chlorine has an atomic number of 17 and a mass number of 35. How many neutrons does it contain?

Accepted Answer

18

Question 5

Which experiment provided evidence that most of the atom is empty space?

Accepted Answer

Rutherford’s gold foil experiment

Question 6

If an atom has 15 protons, 16 neutrons, and 18 electrons, what is its charge?

Accepted Answer

-3

Question 7

Which of the following elements has only one naturally occurring isotope?

Accepted Answer

Sodium

Question 8

The atomic mass of silicon is calculated using its three isotopes: $$^{28}Si (27.9769 u$$, 92.23%), $$^{29}Si (28.9765 u$$, 4.67%), and $$^{30}Si (29.9738 u$$, 3.10%). What is the average atomic mass of silicon?

Accepted Answer

$$28.09 u$$

Question 9

Which statement about atomic number is correct?

Accepted Answer

Atomic number is the number of protons in the nucleus.

Question 10

A forensic scientist uses the ratio of $$^{14}C in $$tooth enamel to estimate the year of birth. This method relies on which property of isotopes?

Accepted Answer

Isotopes have different nuclear properties and abundances.

Question 11

Which of the following is NOT a postulate of Dalton’s atomic theory?

Accepted Answer

Atoms can be subdivided into protons, neutrons, and electrons.

Question 12

Which subatomic particle has a mass of approximately $$1.67 	imes 10$$^{-27}$$ kg and a charge of +1.602 	$$imes $$10^{-19} C$$?

Accepted Answer

Proton

Question 13

If the atomic mass of gallium is 69.723 u, and its isotopes are $$^{69}Ga (68.926 u) $$and $$^{71}Ga (70.925 u$$), which isotope is more abundant?

Accepted Answer

$$^{69}Ga$$

Question 14

Which of the following best explains why atomic masses on the periodic table are not whole numbers?

Accepted Answer

Atomic masses are weighted averages of all naturally occurring isotopes.

Question 15

Which real-world application uses isotope ratios to date biological samples?

Accepted Answer

Carbon dating in archaeology

Question 16

A sample contains 75% $$^{35}Cl (34.969 u) $$and 25% $$^{37}Cl (36.966 u). $$What is the average atomic mass of chlorine in this sample?

Accepted Answer

$$35.46 u$$

Question 17

Which property is the same for all isotopes of a given element?

Accepted Answer

Atomic number

Question 18

Which statement about the nucleus of an atom is correct?

Accepted Answer

The nucleus contains most of the atom’s mass.

Question 19

Which technique is commonly used to measure the abundance of isotopes in a sample?

Accepted Answer

Mass spectrometry

Question 20

If an atom has an atomic number of 8 and a mass number of 18, how many neutrons does it have?

Accepted Answer

10

Atomic Structure and Nuclear Chemistry: Foundations and Applications

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