Question 1

In Rutherford's gold foil experiment (see the first image), most alpha particles passed through the foil with little or no deflection. What did this observation lead Rutherford to conclude about the structure of the atom?

Accepted Answer

Atoms are mostly empty space with a small, dense, positively charged nucleus at the center.

Question 2

In the cathode ray tube experiment (see the second and third images), what evidence indicated that the cathode rays were composed of negatively charged particles?

Accepted Answer

The rays were deflected toward a positively charged plate and away from a negatively charged plate.

Question 3

Millikan's oil drop experiment (see the fourth image) determined the charge of the electron by balancing which two forces on the oil droplets?

Accepted Answer

The upward electric force and the downward gravitational force.

Question 4

The discrete lines in the hydrogen spectrum (see the fifth image) provided evidence for which property of electrons in atoms?

Accepted Answer

Electrons occupy quantized energy levels.

Question 5

According to Bohr's model (see the sixth image), what happens when an electron transitions from a higher energy level ($$n=3) to a $$lower energy level ($$n=2$$)?

Accepted Answer

A photon is emitted with energy $$E = hf$$, where $$E is $$the energy difference between the two levels.

Question 6

Classical physics predicts that an electron orbiting a nucleus (see the seventh image) should continuously emit radiation and spiral into the nucleus. Why does this not happen according to quantum theory?

Accepted Answer

Electrons can only occupy certain quantized orbits where they do not radiate energy.

Question 7

According to de Broglie's hypothesis, what condition must be met for an electron to form a stable standing wave in an atomic orbit (see the eighth and ninth images)?

Accepted Answer

The circumference of the orbit must be an integer multiple of the electron's wavelength: $$2\pi r = n\lambda$$

Question 8

Which of the following best explains why electron orbits in atoms have discrete radii and energy levels (see the tenth image)?

Accepted Answer

Only orbits where the electron's wave closes on itself constructively (standing waves) are allowed.

Question 9

The Schrödinger equation (see the eleventh image) is fundamental to quantum mechanics. What does the wave function $$\psi$$ represent?

Accepted Answer

A mathematical entity whose square gives the probability density of finding a particle at a given location.

Question 10

Which statement best describes the correspondence principle as it applies to quantum mechanics?

Accepted Answer

A new theory must reproduce the verified results of the old theory in the domain where the old theory is known to work.

Question 11

Which experiment provided the first direct evidence for the existence of the atomic nucleus?

Accepted Answer

Rutherford's gold foil experiment.

Question 12

If the wavelength of an electron is given by $$\lambda = \frac{h}{p}$$, where $$h is $$Planck's constant and $$p is $$the momentum, what happens to the wavelength as the electron's speed increases?

Accepted Answer

The wavelength decreases.

Question 13

Which of the following is a direct consequence of the quantization of electron energy levels in atoms?

Accepted Answer

Atoms emit or absorb light at specific wavelengths, producing line spectra.

Question 14

In the context of quantum mechanics, what is the significance of the Ritz combination principle?

Accepted Answer

It relates the frequencies of spectral lines, showing that the sum of the frequencies of two lines often equals the frequency of a third line.

Question 15

Which of the following best describes the progression of atomic models from Bohr to Schrödinger?

Accepted Answer

Bohr's model introduced quantized orbits, de Broglie added wave behavior, and Schrödinger described electrons as wave functions.

Question 16

Which of the following is NOT a prediction of Bohr's model of the atom?

Accepted Answer

Electrons can have any energy and orbit at any distance from the nucleus.

Question 17

Which real-world application relies on the quantization of energy levels in atoms?

Accepted Answer

The operation of lasers, which emit light at specific wavelengths.

Chapter 32: The Atom and the Quantum – Structured Study Notes

Study Guide - Practice Questions

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