Q: Gallium has two naturally occurring isotopes: $$^{69}\mathrm{Ga} (68.926 $$amu, 60.11%) and $$^{71}\mathrm{Ga} (70.925 $$amu, 39.89%). What is the average atomic mass of gallium?

$$(68.926 \times 0.6011) + (70.925 \times 0.3989) = 69.72$$ amu

Question 1

Which of the following statements best describes a major finding from Rutherford's gold foil experiment?

Accepted Answer

Most of the atom is empty space, with a dense, positively charged nucleus at the center.

Question 2

Which subatomic particle was discovered by J.J. Thomson using the cathode ray tube experiment?

Accepted Answer

Electron

Question 3

A silicon atom has an atomic number of 14 and a mass number of 29. How many neutrons does it have?

Accepted Answer

$$29 - 14 = 15$$ neutrons

Question 4

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

Accepted Answer

Atoms can be divided into smaller particles called electrons and protons.

Question 5

Which isotope notation correctly represents an atom with 6 protons and 8 neutrons?

Accepted Answer

$$^{14}_{6}\mathrm{C}$$

Question 6

Gallium has two naturally occurring isotopes: $$^{69}\mathrm{Ga} (68.926 $$amu, 60.11%) and $$^{71}\mathrm{Ga} (70.925 $$amu, 39.89%). What is the average atomic mass of gallium?

Accepted Answer

$$(68.926 	imes 0.6011) + (70.925 	imes 0.3989) = 69.72$$ amu

Question 7

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

Accepted Answer

Atoms are mostly empty space.

Question 8

Which of the following electron configurations is correct for a neutral bromine atom (atomic number 35)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^6$$\ $$4s^2$$\ $$3d^{10}$$\ $$4p^5$$

Question 9

Which statement about isotopes is correct?

Accepted Answer

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

Question 10

Which of the following sublevels can hold a maximum of 10 electrons?

Accepted Answer

d

Question 11

Which equation correctly relates the speed of light ($$c$$), wavelength ($$\lambda$$), and frequency ($$
u$$)?

Accepted Answer

$$c = \lambda 
u$$

Question 12

Which of the following best describes the quantum concept as it applies to energy?

Accepted Answer

Energy is present in small, discrete bundles called quanta.

Question 13

Which of the following statements about the Bohr model of the atom is correct?

Accepted Answer

Electrons orbit the nucleus in fixed, quantized energy levels.

Question 14

Which of the following best describes the shape of a p orbital?

Accepted Answer

Dumbbell-shaped

Question 15

A neutral atom has 17 protons, 18 neutrons, and 17 electrons. What is its atomic number and mass number?

Accepted Answer

Atomic number = 17, Mass number = 35

Question 16

Which of the following statements about the periodic table is correct?

Accepted Answer

The atomic mass is the weighted average of all naturally occurring isotopes.

Question 17

Which of the following best explains why the energy of photons is quantized?

Accepted Answer

Photons can only be absorbed or emitted in discrete energy packets.

Question 18

Which of the following is the correct order of filling for the first five energy sublevels according to increasing energy?

Accepted Answer

$$1s \u003c 2s \u003c 2p \u003c 3s \u003c 3p$$

Question 19

Which of the following statements about atomic structure is correct?

Accepted Answer

Protons and neutrons are located in the nucleus, while electrons are outside the nucleus.

Question 20

Which of the following best describes the difference between the s and d sublevels?

Accepted Answer

The s sublevel can hold up to 2 electrons, while the d sublevel can hold up to 10 electrons.

Models of the Atom: Structure, Subatomic Particles, and Electron Arrangement

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