Atoms are the fundamental building blocks of all matter, composed of a central nucleus containing protons and neutrons, surrounded by rapidly moving electrons.
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let's take a closer look at atoms atoms
are the building blocks that make up
everything all stuff everywhere here
I've got some
drawings this is table salt a solid
here's water a liquid and finally oxygen
gas and what we're looking at here is
what we'd see if we could take these
three things and zoom in zillions and
zillions and zillions of times
and if we could look at these closely
enough we'd be able to see the atoms
these little building blocks that make
everything up now atoms aren't really
little colored circles but it's a good
way to think about them and it's the way
we'll usually draw them when we're
learning about this stuff atoms are
super tiny they are so tiny it can be
really hard to wrap your head around how
tiny they are here is something that
might help you think about this take a
piece of paper look at how wide it is
here all right this is so incredibly
thin now atoms are so small that it
would take one million atoms lined up
next to each other in a row to be as
thick as this tiny width of paper that's
how small atoms are now what I want to
do now is look even closer at an at
let's take one of these atoms here and
zoom in even more so we can see what's
inside of it here's a magnified view of
one atom it's not a perfect
representation of exactly what an atom
would look like but it's close enough
for right now and check this out the
atom itself is made up of even smaller
things right so that we said adoms are
like the building block for all of stuff
but then if you look at an atom it has
even smaller building blocks that make
it up so in the center of the atom is
something called the
nucleus and the nucleus is made up of
two tiny particles there are protons
which I've drawn as red circles here and
then they're neutrons which I've drawn
as blue circles nucleus is here in the
middle of the atom and then on the
outside of the atom there are these uh
little black circles that I'm using to
uh to represent
electrons the electrons you'll see are
connected to these sort of oval paths
and I've drawn these in to show that the
electrons are constantly moving they're
flying around the outside of the atom at
an incredibly high speed whereas the
nucleus stays solid here right in the
middle of the atom now electric charge
is very important when we're talking
about atoms for number number of reasons
protons have a positive charge a proton
has a charge of 1 plus electrons on the
other hand have a negative charge one
electron has a charge of one minus now
neutrons they don't have an electric
charge at all they have a charge of zero
and neutral is a word that we use to
refer to something that doesn't have a
charge so neutrons sounds a lot like
neutral now positive and negative
charges attract remember that opposite
charge is attract and that has important
consequences for how this atom works we
said that these electrons are flying
around the outside of the atom they're
moving really fast so why don't they
just fly out into space well the reason
why is because the negatively charged
electrons are attracted to the
positively charged protons so the
protons kind of pull the electrons in
they keep them from just flying
away but the electrons are moving around
so fast that they're not able to
actually pull in here and actually touch
the protons so that's why they keep
staying on the outside and don't just
crash in here and all touch the
protons now sometimes people ask well
neutrons neutrons don't have a charge
why are they important at all well it
seems that neutrons help keep all of the
particles in the nucleus strongly
connected to each other now electrical
charge is important something else
that's important animportant with atoms
is what their mass is how much they
weigh so in order to figure that out we
have to look at the mass of the various
things that make up the atom now a
proton and a neutron are very very
similar in size and in mass and they
both weigh about this many grams look at
what a tiny number this is right there's
a decimal place all the way over here
this is a number that it's best to
represent in scientific notation instead
but however you write this it's a really
tiny unwieldy number so scientists came
up with another way to uh to measure the
mass of a proton or Neutron and that's
using a unit called the AMU the atomic
mass unit and they said okay one proton
or one Neutron weighs about 1 AMU that's
a lot easier to use than this
measurement here so Proton or Neutron
weighs about 1 Amu an electron on the
other hand is much much much smaller
0549 AMU so a tiny fraction of how much
a Proton or Neutron weighs for this
reason when we're talking about the mass
of atoms which we'll talk about later on
we usually add up the protons and
neutrons to find out how many amus um
the atom weighs and then we usually
don't even worry about the El r at all
because they're just they're so tiny
they don't really have much of an
influence on how much an atom weighs
it's like when you get on a scale to
weigh yourself you don't worry about the
ring you're wearing or whether you're
wearing a necklace or something because
those things are just so tiny they weigh
so little compared to how much you weigh
that it doesn't really influence your
weight so protons and neutrons 1 AMU and
electrons a tiny fraction of that now I
said the atom the way it's drawn here
isn't a perfect representation of what
atoms would actually look like we'll
talk more about that later but there are
two things that I want to bring up for
right now the first is the electrons and
how they move this drawing might make
you think that the electrons are
spinning around in nice circles on the
outside of the atom that's actually not
what happens they're buzzing around much
more randomly kind of like hyperactive
flies all over the place we'll talk more
about that later the second thing has to
do with the size of the nucleus and how
far the electrons are from it If This
Were a real atom blown up many many
times and the nucleus were the size of a
grape the electrons out here would be
almost a mile away have this grap siiz
nucleus and a mile away would be the
electron spinning on the outside so that
means that most of an atom is actually
empty space anyway
now that we've talked about what an atom
looks like and the particles that make
it up we can go and discuss some of the
characteristics that we can use to
describe atoms these are things like
like atomic number mass number and net charge
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