Download Brain Pop Atomic Transcript Shaking, sound of box. Oh a present

Brain Pop Atomic Transcript
Shaking, sound of box. Oh a present.
Dear Tom and Moby, how do we know what atoms look like if we can’t see them? From Darren.
Yeah, atoms are small real small too small to be seen still scientists can do experiments to tell them
things that make up an atom. Right you are my robot pal. You can’t see what’s inside the box, but
shaking it can give you clues to what’s inside. It is the same with atoms. Using indirect means, scientists
have been able to construct different models of the atom. This atomic model has taken years and years
to build and people still tweak it now and then, hopefully making it more and more accurate.
Let’s take a trip through time. At the beginning of the 19th century English man John Dalton built an
atomic model called the atomic theory of matter. Dalton’s model was really a set of ideas. According to
his theory, each type of matter is made up of only one type of atom. For example gold atoms make
gold, iron atoms make iron, and so on. These atoms are way too small to see, so far so good.
About one hundred years after Dalton, J. J. Thomson discovered the electrons. Thomson used a vacuum
tube with metal plates and full pins and an electrical source for his experiment. He found that a beam
would formed between the two plates the cathode and anode. Putting a magnet near the beam caused
it to bend which meant particles of the beam were electrically charged. Thomson discovered that the
cathode ray was made of negatively charged particles called electrons. Because matter is mostly neutral
with no net charge, atoms must contain both positive and negative charges that cancel each other out.
Thomson stated that negatively charged electrons must be stuck all throughout a positive mass. Think
of it like the atom is the cookie dough and the electrons are chocolate chips. The discovery of electrons
was a big deal, but it left questions to be answered, what were the positive particles holding electrons in
place?
In 1909, Rutherford and his team set out to answer some of those questions. They beamed positively
charged alpha particles at a sheet of really thin gold foil. Because so many particles could pass right
through the thin gold foil; Rutherford hypothesized that the gold atoms mostly to be made of empty
space. But some of the particles did bounce off so Rutherford revised his hypothesis to say a gold atom
must have some very small positive charge he named this mass the nucleus. He called the positively
charge nucleus particles protons and said the electrons were scattered in empty space around the
nucleus.
James Chadwick, a student of Rutherford’s found new particles in the nucleus that were not affected by
an electric field at all. Alpha particles in the experiment had knocked them lose. Chadwick’s called
these uncharged particles neutrons. Also in the early 20th century, scientists discovered that electrons
are arranged in energy levels; the lower energy levels are closest to the nucleus and can only hold just a
few electrons. The higher energy levels are farther away and can hold more electrons. Electrons are so
small and quick that their energy levels are not neat planet like orbits around the nucleus. Instead they
exist in a region called the electron cloud. The atomic model is constantly evolving as scientists discover
more and more about what make the universe tick.
Oh okay, go ahead and open it. Hey it is an atomic model. Well you have to put it together. That’s not
right.