|Section 1.6 -
|According to classical physics, the orbiting negatively
charged electron should eventually run out of energy and collapse into the
positively charged nucleus. From observation, we see that matter is
very stable. We therefore infer that electrons do not collapse into
the nuclei of atoms. Rutherford's model of the atom could not explain
|In Bohr's and Rutherford's models, the atom consists
of a nucleus, with protons having a positive charge and neutrons carrying
zero charge, surrounded by empty space. In Rutherford's model, the
electrons orbit the nucleus like planets around the Sun. In Bohr's
model, the electrons are found in fixed energy levels around the nucleus.
The first energy level holds a maximum of two electrons, while the second
energy level holds a maximum of eight electrons. The amount of potential
energy an electron has depends upon the energy level it occupies.
|Spectroscopy revealed that all the elements have
characteristic line spectra. Bohr came up with his model of the atom
to explain these observations. Spectroscopy provided the empirical
evidence upon which Bohr's model is based.
|An electron in its ground state is in the lowest
possible energy level, where it is the most stable. At this energy level,
the electron does not emit any electromagnetic radiation because it cannot
drop to a lower energy level. When an electron is in the excited state,
it has absorbed energy and is in a higher energy level. An electron in the
excited state can drop to a lower energy level and release a fixed amount
of energy as electromagnetic radiation that appears in a line spectrum.
|Bohr's atomic model could only explain the line
spectrum of hydrogen. It could not accurately predict the line spectra
of more complex elements.
|An electron in a lower energy level has less
energy than an electron in a higher energy level. therefore, when an
electron drops from a higher energy level to a lower energy level, it emits
the excess energy in the form of light
|Energy levels have a specific energy value. Electrons
in the same energy level have the same amount of energy. To jump to
a higher energy level, they must absorb a specific amount of energy. To
drop to a lower energy level, they must release a specific amount of energy.
electrons cannot be found in between energy levels.
|Plug one of the discharge tubes into an electrical
source. Observe the gas discharge tube through a spectroscope and record
the lines spectrum of the tube. To determine the identify of the gas,
compare its line spectrum to the line spectra of identified gases in a resource.
Repeat for the second discharge tube.
|In bohr's atomic model, electrons can only possess
specific amounts of energy, depending on the energy level in which that are
found. When electrons of an element are excited, they always jump to
specific higher energy levels. When electrons drop to lower energy
levels, they always release specific amounts of energy, equal to the difference
between the higher and lower energy levels. Since each element has
a unique electron configuration, it has a characteristic line spectrum.