Chapter 7 - Quantum Theory and Atomic Structure

Question 1

Speed of light (c)

Answer 1

3.00 x 10⁸ m/s

Question 2

Frequency (v)

Answer 2

Number of complete waves or cycles that pass a given point per second expressed as a Hertz; cycles/second

Question 3

Wavelength (λ)

Answer 3

Distance a wave travels in 1 cycle

Question 4

Visible light spectrum

Answer 4

400 (violet) - 750 nm (red) wavelength range

Question 5

Electromagnetic spectrum

Answer 5

Wavelength and frequency have an inversely proportional relationship: the longer the wavelength, the lower the frequency, the shorter the wavelength, the higher the frequency; in increasing wavelength order:

gamma < x-ray < ultraviolet < visible light < infrared < microwave < radio waves

Question 6

Planck’s constant (h)

Answer 6

h = 6.626 x 10^-34 J*s

Question 7

Refraction

Answer 7

A phenomenon in which a wave changes its speed and therefore its direction as it passes through a phase boundary into a different medium; waves refract, particles do not refract

Question 8

Dispersion

Answer 8

A type of refraction where white light disperses into its component colors when it passes through a prism (or any refracting object) because each incoming wave is refracted at a slightly different angle

Question 9

Diffraction

Answer 9

The phenomenon in which a wave striking the edge of an object bends around it; a wave passing through a slit as wide as its wavelength forms a circular wave; only works with waves

Question 10

Destructive interference

Answer 10

When waves of light pass through 2 adjacent slits, the nearby circular waves interact through the process of interference; the crests coincide with troughs and the amplitudes cancel to form a darker region

Question 11

Constructive interference

Answer 11

When waves of light pass through 2 adjacent slits, the nearby circular waves interact through the process of interference; crests of the waves coincide in phase and the amplitudes add together to form a brighter region

Question 12

Blackbody radiation

Answer 12

Solid object emits visible light when it is heated to about 1000K; changes in intensity and wavelength of emitted light as an object is heated is characteristic of blackbody radiation; ie. at a temperature of about 2000K, an object emits bright white light

Question 13

Quantum theory

Answer 13

Since the hot objects emits only certain quantities of energy, and the energy must be emitted by the object’s atoms, each atom emits only certain quantities of energy; the energy of the an atom is quantized: it occurs in fixed quantities rather than being continuous

Question 14

Quantum of energy equation

Answer 14

Question 15

Photoelectric effect

Answer 15

Explains the flow of current when light strikes a metal; for a current to flow, the light shining on the metal must have a minimum frequency and different metals have different minimum frequencies; current flows the moment light of the minimum frequency shines on the metal, regardless of the light’s intensity

Question 16

Photon theory

Answer 16

He proposed that light itself is particulate, quantized into tiny “bundles” of energy called photons; each atom changes its energy by an amount of (delta)E when it absorbs or emits one photon, one “particle” of light, whose energy is related to its frequency and not its amplitude (or intensity)

Question 17

Line spectrum

Answer 17

When light from electrically excited gaseous atoms passed through a slit and is refracted by a prism, it creates a line spectrum: a series of fine lines at specific wavelengths (specific frequencies) separated by black spaces; not a continuum of the entire spectrum

Question 18

Rydberg equation

Answer 18

n = arbitrary whole integer, R = Rydberg constant

R = 1.0967 x 10⁷ m^-1

Question 19

Bohr model of the Hydrogen atom

Answer 19

The H atom has only certain energy levels, which Bohr called stationary states (one circular orbit); the atom changes to another stationary state (electron moves to another orbit) only by absorbing or emitting a photon; the H atom absorbs a photon when an electron moves to an outer (higher energy) orbit; the H atom emits a photon when an electron moves to a lower energy orbit (closer to the nucleus)

Question 20

de Broglie wavelength

Answer 20

Matter behaves as though it moves in a wave; an object’s wavelength is inversely proportional to its mass so heavy objects such as planets and baseballs have wavelengths many orders of magnitude smaller than the object themselves, too small to be detected

h = Planck’s constant, u = speed of object, m = mass of object

Question 21

Heisenberg’s uncertainty principle

Answer 21

Werner Heisenberg postulated that it is impossible to know simultaneously the position and momentum (mass x speed) of a particle

(delta) x = uncertainty in position, (delta) u = uncertainty in speed