Question 1

Which statement best describes the law of definite composition as proposed by Dalton?

Accepted Answer

The mass ratio of elements in a compound is always the same, regardless of the sample.

Question 2

According to Dalton’s Atomic Theory, which of the following statements is still accepted today?

Accepted Answer

Compounds contain atoms in small whole number ratios.

Question 3

Which experiment led Rutherford to propose the existence of a dense nucleus in the atom?

Accepted Answer

Firing alpha particles at thin gold foil and observing some particles deflected backward.

Question 4

An atom of $$^{29}\mathrm{Si}$$ has how many neutrons?

Accepted Answer

15

Question 5

Which of the following is true about isotopes?

Accepted Answer

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

Question 6

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

Accepted Answer

$$69.72\ \mathrm{amu}$$

Question 7

Which statement about the Thomson 'plum pudding' model is correct?

Accepted Answer

Electrons are distributed evenly throughout a sphere of positive charge.

Question 8

Which subatomic particle was discovered by James Chadwick?

Accepted Answer

Neutron

Question 9

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

Accepted Answer

Atoms are mostly empty space.

Question 10

What is the maximum number of electrons that can occupy the third energy level of an atom?

Accepted Answer

18

Question 11

Which electron configuration represents bromine ($$Z=35$$)?

Accepted Answer

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

Question 12

Which of the following statements about the quantum mechanical model of the atom is correct?

Accepted Answer

Electrons are most likely found in regions of space called orbitals.

Question 13

Which sublevel can hold a maximum of 10 electrons?

Accepted Answer

d

Question 14

Which of the following best describes the relationship between wavelength and frequency for light?

Accepted Answer

As wavelength increases, frequency decreases.

Question 15

Which element has more electrons in its outermost d sublevel: Chromium ($$Z=24) or $$Manganese ($$Z=25$$)?

Accepted Answer

Manganese

Question 16

Which of the following is a real-world application of emission line spectra?

Accepted Answer

Identifying elements in distant stars using their atomic fingerprints.

Question 17

Which orbital has a spherical shape?

Accepted Answer

s orbital

Question 18

If an atom has 17 protons and 20 neutrons, what is its mass number?

Accepted Answer

$$37$$

Question 19

Which of the following best describes the quantum concept of energy?

Accepted Answer

Energy is lost or gained in small, discrete bundles called quanta.

Question 20

Which of the following is NOT a correct statement about subatomic particles?

Accepted Answer

Electrons are located inside the nucleus.

Models of the Atom: From Dalton to Modern Atomic Theory

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