Basic Nuclear and Atomic Physics-Atomic Structure


Now let’s look at how atoms are put together
because you need to have a good picture of for when start talking about detecting radiation. An atom has a nucleus, and this nucleus
is surrounded by the same number of electrons as there are protons in the nucleus
let’s look. This is not the picture you thought you would
see I bet. These are pictures taken by voyager,
looking back as it’s leaving our solar system. Notice how dim the sun is. And how closely the inner planets are clustered
around the sun. NASA also has this diagram, to explain what
it is we are looking at. There seems to be mostly nothing there, and
gosh knows that’s true. It’s sobering to think about how little
matter there is in our solar system. And how brilliant the NASA folks have to be
to even find these specks of planets somewhere in the vastness of space. How about an atom? Now let’s look at a gold atom, Gold is pretty
heavy right? The density of gold nuclei is roughly 2.3
times ten to the 17 kilograms per cubic meter meaning, most of the atom is empty. On the other hand the next gold nucleus is
on the order of 6 miles away depending on the bonding, which is very different
from how stars are laid out Neutrons show that this emptiness in atoms
is true. Think about how often you would have to shoot
a laser beam at random into the solar system to finally hit the sun. The mean path of a neutron is often over ten
centimeters and for aluminum is 72 centimeters. How many atoms did the neutron go through? Now let’s use aluminum because it’s atomic
mass is 27 and it’s density is 2.7 grams per cubic centimeter
and that makes the math easy. How many atoms are there in a line along 72
centimeters? Well, let’s see. One cubic centimeter weighs 2.7 grams, therefore
it contains a tenth of a mole, This one cubic centimeter then contains 6.022
times ten to the 22nd aluminum atoms. This means each aluminum atom occupies 1.66
times ten to the minus 23rd cubic centimeters. Now let’s let the atoms be contained inside
of cubes so the diameter of a single aluminum atom,
is the cube root of this number or 2.55 times ten to the minus eighth
If we lined all of these atoms up then a neutron would pass through 3.92 times
ten to the seventh atoms per centimeter or about 2.8 billion atoms in 72 centimeters. A neutron, on average goes through 28 billion
atoms before it collides with a nucleus. Now do you believe that atoms are mostly nothing? Why don’t we fall through the earth? Or why can’t we walk through walls? That has to do with the electrons and the
columbic forces, which is a story for later. Let’s go build the universe, proton by proton.

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1 Response

  1. Asrat Mengesha says:

    Atoms don't exist, man!.
    If atoms exist, if atoms are real, components of atoms exist, if electrons, protons, neutrons, positrons, quarks, bosons,Higgs boson…..etc exist for real, then, what a hell make you represent them by computer simulation? Why are yu not showing us as they are as the electrons….etc.revolve the nucleus….etc? because you just full us and atoms don't exist. right?
    Thanks.

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