c. Structure of Water. The properties of water may best be explained by
examining the structure of the water molecule. The water molecule consists of two
hydrogen atoms bonded covalently to one oxygen atom. The three atoms are bound
together as shown below.
O
H
H
This arrangement leads to an electron-rich atom, oxygen, on one end and two electron-
poor atoms, hydrogen, on the other end. This results in a molecule that resembles a
bar magnet in that it has a negative pole and a positive pole, as shown below.
_
O
H
H
+
+
Actually, there are not distinct electrical charges on the molecule, only partial charges,
referred to as δ+ and δ- (the Greek letter delta, δ, meaning partial). While these charges
are only partial, they are still strong enough for water to be referred to as a polar
molecule, meaning that it has a positive and negative end.
d. Hydrogen Bond. The polarity of the water molecule gives rise to an unused
type of bond between water molecules, the hydrogen bond. This bond is the electrical
attraction between the partially negative oxygen atom of one molecule and the partially
positive hydrogen atom of another molecule.
δ-
H
δ+ - - - - δ-
O
H
H
H
O
O
δ+
H
H
δ-
H
O
H
MD0803
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