Isotopes: atoms of the same element that have different numbers of neutrons.
Example: Carbon atoms that have 7 or 8
neutrons instead of the usual 6.
Example: Hydrogen atoms normally have
___________ neutrons in their nucleus. There
are 7 different isotopes of Hydrogen, though!
Hydrogen 1 has ___ neutrons.
Hydrogen 2 has ___ neutron, it’s called deuterium.
Hydrogen 3 has ___ neutrons, it’s called tritium.
Hydrogen 4 is a highly unstable isotope of hydrogen, it
has ____ neutrons. Hydrogen 5 has ____ neutrons, Hydrogen 6 has ____ neutrons and Hydrogen 7 has ____
neutrons. All of these are isotopes of hydrogen, but they all have exactly 1 proton, so they are definitely
hydrogen!!!
What is it?
“Heavy” water is a form of water with a unique atomic structure and properties coveted for the production of
nuclear power and weapons. Like ordinary water—H20—each molecule of heavy water contains two hydrogen
atoms and one oxygen atom. The difference, though, lies in the hydrogen atoms. In ordinary water, each
hydrogen atom has just a single proton in its nucleus. In heavy water, each hydrogen atom is indeed heavier,
with a neutron as well as a proton in its nucleus. This isotope of hydrogen is called deuterium, and heavy
water's more scientific name is deuterium oxide, abbreviated as D20. Note: ice cubes made with “heavy water”
will sink in water, a testimony to the fact that they are indeed “heavy” or more dense! Heavy water in small
amounts is harmless, however, in large amounts “heavy water” is poisonous, even though it’s just H2O!
Draw a normal water molecule, and draw a “heavy” water molecule that has deuterium instead of regular
hydrogen:


What is the molecular weight of a normal water molecule? _____________ (add up the weight of the
atoms involved)
What is the molecular weight of a “heavy water” molecule made with deuterium instead of hydrogen?
_____________ (add up the weight of the atoms involved)
Define: What’s heavy water??? _________________________________________________________
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