Expt 9 Light from Atoms
How does an atom rapidly decay back to its ground state?
by releasing energy in the form of light
How is wavelength and frequency related?
c = wavelength x frequency
What does n1 and n2 represent in the mathematical description of the hydrogen atom spectrum?
energy levels (prinicple quantum numbers)
For each atom which undergoes a transition from an excited state to a ground state how many photons are released with the transition energy, delta E?
one
In the ground state, all of the electrons of atom M occupy orbitals with the lowest possible energy according to
the Aufbau principle
The energy and frequency of the light which is released during the decay transition depend on
the difference in energy (delta E) between the ground state and the excited state
Planck's equation gives the relationship between
the energy of a light photon (E) and its frequency (v)
The origin of colors associated w/ certain elements lies in
the excitation of atoms by heat energy or electrical energy and the subsequent release of the excitation energy as photons of light.
The color we perceive depends on
the wavelengths of the photons present
What is Rydberg's constant?
(3.25 x 10^15 Hz)
What is the speed of light?
3.0 x 10^10 cm/sec
What is Planck's constant?
6.63 x 10^-34 Js/photon
What is Planck's equation?
E = h x v
The energy of a photon can be related to the wavelength by
E = hc/lambda
spectroscope
a device that separates the individual wavelengths present in light, usually via diffraction
When the atom absorbs enough energy, one or more of the valence electrons moves to
a higher energy orbital
What are the two forms of commercial light that were examined in the expt?
fluorescent and incandescent
Which energy level is higher in the mathematical description of the hydrogen atom spectrum?
n2 is the higher energy level and n1 is the lower energy level
Since every atom has many higher energy levels to which an electron may be excited, the light emitted from the various excited atoms will consist of
several different energies or frequencies
What metal chloride solutions were used in the flame test?
sodium, potassium, calcium, strontium, and copper
A more detailed study of the light emitted from excited atoms can be done using a
spectroscope
mathematical description of the hydrogen atom spectrum
v = R(1/n1^2 - 1/n2^2)
When is an atom in its excited state?
when it has a higher energy than its ground state (when one or more of the valence electrons moves to a higher energy orbital)
If a particular set of photons emitted from an excited state element has a wavelength that falls within the visible spectrum (400-800nm), will our eyes detect the light?
yes
