Q: A sample of chlorine contains 75.37% $$^{35}Cl ($$atomic mass = 34.969 u) and 24.63% $$^{37}Cl ($$atomic mass = 36.966 u). What is the average atomic mass of chlorine?

$$(0.7537 \times 34.969) + (0.2463 \times 36.966) = 35.45 u$$

Q: If silicon has three isotopes: 92.23% $$^{28}Si (27.9769 u$$), 4.67% $$^{29}Si (28.9765 u$$), and 3.10% $$^{30}Si (29.9738 u$$), what is the average atomic mass of silicon?

$$(0.9223 \times 27.9769) + (0.0467 \times 28.9765) + (0.0310 \times 29.9738) = 28.09 u$$

Question 1

Which experiment provided evidence that most of the mass of an atom is concentrated in a tiny, positively charged nucleus?

Accepted Answer

Rutherford's gold foil experiment

Question 2

Which subatomic particle has a mass of $$9.109382 	imes 10$$^{-31}$$ kg and a charge of -1.602176$$ 	imes $$10^{-19} C$$?

Accepted Answer

Electron

Question 3

A neutral atom of gold has 79 protons, 118 neutrons, and 79 electrons. What is its mass number?

Accepted Answer

$$197$$

Question 4

Which statement about isotopes is correct?

Accepted Answer

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

Question 5

Which law states that the total mass of reactants equals the total mass of products in a chemical reaction?

Accepted Answer

Law of conservation of mass

Question 6

A sample of chlorine contains 75.37% $$^{35}Cl ($$atomic mass = 34.969 u) and 24.63% $$^{37}Cl ($$atomic mass = 36.966 u). What is the average atomic mass of chlorine?

Accepted Answer

$$(0.7537 	imes 34.969) + (0.2463 	imes 36.966) = 35.45 u$$

Question 7

Which real-world application uses isotope ratios to determine the year of birth from tooth enamel?

Accepted Answer

Forensic dating using $$^{14}C $$levels

Question 8

What is the charge of an atom with 15 protons and 18 electrons?

Accepted Answer

$$-3$$

Question 9

Which process is illustrated by the splitting of $$^{235}U $$after absorbing a neutron, releasing energy and forming $$^{92}Kr $$and $$^{141}Ba$$?

Accepted Answer

Nuclear fission

Question 10

Which instrument is used to separate isotopes based on their mass-to-charge ratio?

Accepted Answer

Mass spectrometer

Question 11

If silicon has three isotopes: 92.23% $$^{28}Si (27.9769 u$$), 4.67% $$^{29}Si (28.9765 u$$), and 3.10% $$^{30}Si (29.9738 u$$), what is the average atomic mass of silicon?

Accepted Answer

$$(0.9223 	imes 27.9769) + (0.0467 	imes 28.9765) + (0.0310 	imes 29.9738) = 28.09 u$$

Question 12

Which element is defined by having 6 protons in its nucleus?

Accepted Answer

Carbon

Question 13

Which of the following is a correct statement about Dalton's atomic theory?

Accepted Answer

Atoms of a given element are identical in mass and properties.

Question 14

A sample contains two isotopes of gallium: $$^{69}Ga (68.926 u) $$and $$^{71}Ga (70.925 u). $$The average atomic mass is 69.723 u. Which isotope is more abundant?

Accepted Answer

$$^{69}Ga$$

Question 15

Which of the following best explains why most alpha particles pass straight through gold foil in Rutherford’s experiment?

Accepted Answer

Most of the atom is empty space

Question 16

Which isotope of hydrogen contains one proton and two neutrons?

Accepted Answer

$$^{3}H$ (tritium)$$

Question 17

Which of the following is NOT a modification to Dalton’s atomic theory based on modern discoveries?

Accepted Answer

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

Question 18

Which real-world application uses technetium ($$^{99}Tc) in $$medicine?

Accepted Answer

Medical imaging for diagnostic scans

Question 19

Which of the following best describes the law of constant composition?

Accepted Answer

A given compound always contains the same elements in the same proportion by mass.

Question 20

Which of the following is the correct formula for calculating the percent abundance of an isotope?

Accepted Answer

$$	ext{percent abundance} = \frac{	ext{number of atoms of isotope}}{	ext{total number of atoms of element}} 	imes 100$$

Atomic Structure and Isotopes: Foundations of Modern Chemistry

Study Guide - Practice Questions

Study Guide - Flashcards