|In water, why don't the hydrogen and oxygen
|Question Date: 2013-03-07|
Hydrogen and Oxygen do not separate in water
because the energy of a water molecule
H2O is less than the energy of
separate H and O atoms. Nature always like to go
to the minimum energy state; nature can be
The water molecule (H2O) is held
together by covalent bonds. A covalent bond is
formed when two atoms share a pair of electrons
between them. Covalent bonds are lower in energy
than the corresponding separated atoms. This is
because when two atoms come close to each other,
the atomic orbitals of the atoms overlap and mix
to form molecular orbitals. Two atom orbitals
which overlap will mix to make two molecular
orbitals (one with lower energy than the
isolated atomic orbitals (bonding) and one with
higher energy than the isolated atomic orbitals
(antibonding)). If each atom contributes one
electron to the bond, then the electrons can
spin pair (one is spin up and the other is spin
down) and move to the lower energy state that is
the spin-paired bonding molecular orbital. Since
covalent bonds are lower in energy than the
corresponding separated atoms, the atoms stay
bonded together rather than separating.
In water, hydrogen and oxygen are held
together by chemical bonds. These bonds are
strong, so in most of the conditions we
encounter, hydrogen and oxygen don't separate.
However, these bonds are not impossible to
break. In fact, if you apply electricity of a
proper current and voltage, you will split water
to form hydrogen gas and oxygen gas!
Hydrogen in water is chemically bonded to
oxygen. It takes energy to get them to separate,
just as it releases energy (in the form of heat)
to unite them.
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