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CHEMISTRY
Ions, Water and Gram Molecular Weights
ATOMIC NUMBER AND
IONS
Atomic number = the number of protons in an atom
It also = the number of electrons normally.
If an atom loses an electron, it gains a positive charge
(since a negative left) and is called a cation
(pronounced “cat-ion”)
if an atom gains an electron, it gets a negative charge
(since a negative electron was added and is called an
anion (pronounced “an-ion”).
IONS AND WATER
Hydrogen is also prone to getting a slight negative
charge if its electrons are more attracted to the other
atom in a compound, like when it combines with
oxygen to create water.
The hydrogens have a slightly positive charge and
the oxygen has a slightly negative charge.
These partials can attract each other and make water
molecules “stick” to each other.
IONS AND WATER
They line up like this:
Look familiar? The angles here lead to the angles
seen in solid water: Snow!
IONS AND WATER
This also explains why water is “sticky” enough to
Form beads
Form puddles
Have surface tension
Dissolve a large number of other compounds that
have partial charges like salts...
GRAM MOLECULAR
WEIGHT
There’s another interesting thing you find about
chemicals - you can know how many atoms or
molecules of an element or compound by using
something called the gram molecular weight.
The same number of grams of an element as the
number in its atomic weight contains
602,000,000,000,000,000,000,000 atoms.
This amount of an element is called a mole.
GRAM MOLECULAR
WEIGHT
602,000,000,000,000,000,000,000 (602 sextillion) can
also be written in scientific notation as 6.02 x 1023
Want 6.02 x 1023 atoms of carbon, atomic weight 12?
Easy! Get 12 grams of it.
Want 6.02 x 1023 atoms of gold, atomic weight 196?
Easy! Get 196 grams of it.