Hey there folks, we're excited to be launching a brand new series called
Chemistry Basics. We figured it's about time to get you the real nitty gritty on
some serious chemistry topics like isotopes and radioactivity, the periodic
table, the pH scale, and a whole bunch of other fascinating stuff. When one of
these topics comes up in a Reactions video, we're gonna link directly to the
Chemistry Basics video so you can get that extra dose of chemical knowledge.
In the meantime, the videos will exist over here in a playlist.
So here's the first episode. We sure hope you love it.
So you've heard about isotopes, but what exactly are they? You probably know that atoms have
a dense nucleus made up of positively charged protons and neutral neutrons, and that the nucleus is
surrounded by a bunch of negatively charged electrons. Isotopes are atoms of
the same element, meaning to have the same number of protons and electrons, but
that have different numbers of neutrons. The differing numbers of neutrons give
isotopes different masses. Back in the early 1900's, the discoverer of the
electron, J.J. Thomson, with the help of the student
Francis W. Aston, identified two different types of neon atoms. One type with 10
protons, 10 electrons, and 10 neutrons. And then one with 10 protons, 10 electrons, and
12 neutrons. Aston went on to invent a groundbreaking machine that he called a
mass spectrograph. Using this machine, Aston identified hundreds of other
isotopes of other elements. The mass spectrometer is now used in labs all
over the world, and Aston won the 1922 Nobel Prize in Chemistry for his work.
These are the isotopes of neon that Thomson and Aston saw. The numbers
you see here tell you the total number of protons plus neutrons in each atom,
and they also tell you the isotope's approximate mass. Technically, the mass of
an atom would include protons, neutrons, and electrons, but since the mass of an
electron is almost two thousand times less than that of protons and neutrons,
we can basically ignore them. When it comes to atoms and their behavior,
there's an important distinction to make between chemical reactions and nuclear
reactions. Chemical reactivity is defined by the electrons that atoms possess.
When atoms come into contact with one another, it's their outer electrons that interact
and determine the type and the intensity of the reaction. Since isotopes of a
given element have the same number of electrons, they will undergo similar
reactions. On the other hand, nuclear reactions rely on the particles in the
nucleus. So different isotopes will undergo different nuclear reactions
because of the differences in the makeup of their nuclei. So what happens in a
nuclear reaction? Basically something changes in the nucleus. Because the
nucleus is made up of protons and neutrons, you might think that all of
those positive charges crammed together and repelling one another would make the
nucleus unstable. Luckily there's a force known as the
Strong Nuclear Force that acts as the glue that holds the whole thing together.
But when the nucleus of an atom contains lots of protons and neutrons, or when
certain neutron to proton ratios exist, even the Strong Nuclear Force can't hold
it all together, and the whole thing can become unstable. When that happens, the
atom's nucleus will either kick out some particles or rearrange itself. Typically
one of three things happens. Alpha Decay is when two neutrons and two protons are
kicked out of the nucleus to form two different species: a helium nucleus and a
totally different element than the one we started with. In this case uranium
ejects the alpha particle and becomes thorium. In Beta Decay a neutron splits
into a proton and an electron, and the electron is ejected from the nucleus.
Because this changes the number of protons in the nucleus, a new element is
formed. In this case thorium becomes protactinium. Gamma Decay is when protons
and neutrons in the nucleus are rearranged to reduce the energy of an
unstable atom. These rearrangements come with the release of energy in the form
of gamma rays. This time, since the number of protons in the nucleus stays the same,
no new element is formed. These spontaneous changes in nuclei are known
as radioactivity. While radioactive substances can be hazardous, in some
cases they can also be incredibly useful. They give us an accurate way to tell how
old things are, they can be used to detect leaks in pipes, or even see where
certain medicines go in your body.
Thanks for watching, and make sure to check out the other videos in this series here.