EARLY ATOMIC THEORIES AND THE ORIGINS
OF QUANTUM THEORY
Section 3.1 Answers
1. Electron/scanning
2. Electron charge
3. D
4. a) 6 electrons, 7 neutrons
b) 7 e, 7n
c) 19 e, 22 n
d) 30 e, 36 n
5. atomic number is same but atomic masses are different
6. a) 41K19
b) 14N7
c) 59Co27
d) 102Ru44
7 a) 63Cu2+29
b) 32S2-16
9. Alpha, beta and gamma
10. c
Plancks Theory
11.
In 1900 Max Planck proposed a formula. Instead of allowing
energy to be continuously distributed among all frequencies,
Planck's model required that the energy in the atomic
vibrations of frequency f was some integer times a small,
minimum, discrete energy,
Emin = hf
where h is a constant, now known as Planck's constant,
h = 6.626176 x 10-34 J s
Planck's proposal, then requires that all the energy in the
atomic vibrations with frequency f can be written as
E=nhf
where n in an integer, n = 1, 2, 3, . . . No other values of the
energy were allowed. This idea that something -- the energy in
this case -- can have only certain discrete values is
called quantization.
Photon Energies for EM Spectrum
Answer 12. In 1905 Albert Einstein provided a daring
extension of Planck's quantum hypothesis and was able to
explain the photoelectric effect in detail.
Expanding on Planck's quantum idea, Einstein proposed that
the energy in the light was not spread uniformly throughout
the beam of light. Rather, the energy of the light is contained
in "packets" or quanta (the plural of quantum, a single
"packet") each with energy of
E=hf
where again h is Planck's constant and f is the frequency of
the light. All of the energy in one quantum -- now called
a photon -- is given to one electron.
Planck’s Law
Every physical body spontaneously and continuously emits electromagnetic
radiation. Near thermodynamic equilibrium, the emitted radiation is nearly
described by Planck's law. Because of its dependence on temperature, Planck
radiation is said to be thermal. The higher the temperature of a body the more
radiation it emits at every wavelength. Planck radiation has a maximum
intensity at a specific wavelength that depends on the temperature. For
example, at room temperature (~300 K), a body emits thermal radiation that is
mostly infrared and invisible. At higher temperatures the amount of infrared
radiation increases and can be felt as heat, and the body glows visibly red. At
even higher temperatures, a body is dazzlingly bright yellow or blue-white and
emits significant amounts of short wavelength radiation,
including ultraviolet and even x-rays. The surface of the sun (~6000 K) emits
large amounts of both infrared and ultraviolet radiation; its emission is peaked
in the visible spectrum.
In the interior of a physical medium, radiation can be absorbed and emitted by
matter. This mediates transfer of energy as heat, and can change the internal
energy of the matter, and the occupation numbers of the states of its
molecules.
Planck radiation is the greatest amount of radiation that any body at thermal
equilibrium can emit from its surface, whatever its chemical composition or
surface structure. Passage of radiation across an interface between media can
be characterized by the emissivity of the interface, the radiance of the passing
radiation divided by the Planck radiance. It is in general dependent on chemical
composition and physical structure, on temperature, on the wavelength, on the
angle of passage, and on the polarization, of the radiation