Exploring Radiation:
Mapping the Atom
Ernest Rutherford had led a trail to the heart of the atom. They now
knew about the positively charged nucleus containing protons. The focus
of Nuclear physics was shifted to the behavior and structure of electrons.
Throughout the 1920's, Danish physicist Niels Bohr would work with other
scientists to develop new way indeed of looking at electrons.
Niels Bohr was born in Denmark and which he was in University he did
research on the possible arrangements of electrons on the surface of atoms
of metals. Bohr studied the arrangements of electrons around the nucleus
and needed an explanation in finding what would prevent the electrons from
falling into the nucleus instead of circling around. He found the idea
of quantum - a fixed unit of energy.
As a body is heated, it gives out light. As the temperature increases,
the light coming from it not only has more energy but its wavelengths
grow shorter. This is why a piece of metal when heated changes from red
to yellow and then to white. Our eyes perceive color based on the wavelengths
of light. Red has the longest wavelength followed by yellow, blue and white.
From the 19th century scientists new that glowing material was actually
a mixture of wave lengths and though that these were given out continuously.
What Bohr's scientists found was that the wave radiation was given out
in spurts called quantum.
Using this idea of quantum Bohr found an idea which could explain why
electrons didn't spiral and fall into the atom's nucleus.
He said that an electron must always have an angular movement (the energy
of orbiting) and it was equivalent to an integer (any whole number) times
h(Planck's constant) divided by 2'pi'. Because the energy
determines the location of the orbit this in turn meant that the electron
could only be in a fixed amount of orbital paths. Unlike a car, the electron
can not change to a faster or slower lane. When light, heat, or some other
kind of energy hits an atom, it can cause an electron to instantly jump
from one orbit to another further away. Similarly an electron can jump
back into an inner one, sending our quantum energy.
While Bohr's worked with the hydrogen atom, it could not accurately
predict more compilcated ones. Two different approaches were tried. In1923,
the French physicist Louis de Broglie suggested that just as a wave had
particle properties, maybe a particle had wave properties. Experiments
found startling evidence about the wavelike behavior of electrons. In 1925,
German physicist Werner Heisenberg created a different approach to the
quantum theory. Instead of trying to visualize how electrons moved, he
compiled sets of numbers that represents various properties of electrons.
Eg: spin, energy, and momentum.
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