Geoscience Reference
In-Depth Information
Table 1.4.
Structures of some common compounds
Structure showing
bonds and free
electrons
Formula with
free electrons
Formula without
free electrons
Compound name
OO
Molecular oxygen
O
2
(g)
O
2
(g)
Molecular nitrogen
NN
N
2
(g)
N
2
(g)
O
Ozone
O
3
(g)
O
3
(g)
O
O
OH(g)
Hydroxyl radical
OH
OH(g)
H
H
Water vapor
O
H
2
O(g)
H
2
O(g)
NO(g)
Nitric oxide
NO
NO(g)
N
+
NO
2
(g)
Nitrogen dioxide
NO
2
(g)
O
O
S
Sulfur dioxide
SO
2
(g)
SO
2
(g)
O
O
CO
+
Carbon monoxide
CO(g)
CO(g)
Carbon dioxide
OCO
CO
2
(g)
CO
2
(g)
H
HC
H
Methane
CH
4
(g)
CH
4
(g)
H
O
OO
S
SO
4
2
−
SO
4
2
−
Sulfate ion
O
afreeelectron are called
free radicals
and are highly
reactive. Some non-free radicals that have a single bond
[e.g., O
3
(g)] are also reactive because single bonds are
readily broken. Compounds with triple bonds [N
2
(g)
and CO(g)] are not so reactive because triple bonds are
difficult to break.
Noble elements
(He, Ar, Ne, Kr, Xe)
have no free electrons and no potential to form bonds
with other elements; thus, they are chemically unreac-
tive (inert).
Forsome compounds in Table 1.4 [NO
2
(g), O
3
(g),
CO(g)], positive and negative charges are shown. Such
a charge distribution arises when one atom transfers
charge to another atom during molecular formation.
During NO
2
(g) formation, for example, a net nega-
tive charge is transferred to an oxygen atom from the
nitrogen atom, resulting in the charge distribution
shown. Compounds with both positive and negative
charges have zero net charge and are not ions, but
the positive (negative) end of the compound is likely
to attract negative (positive) charges from other com-
pounds, enhancing the reactivity of the compound. For
SO
4
2
−
,anet negative charge is shown, indicating that
it is an ion.
When oxygen combines with an element or com-
pound during a chemical reaction, the process is called
oxidation
, and the resulting substance is
oxidized
.The
gases O
2
(g), O
3
(g), OH(g), H
2
O(g), NO(g), NO
2
(g),
SO
2
(g), CO(g), and CO
2
(g) are all oxidized gases.
When oxygen is removed from a substance during a
reaction, the process is called
reduction
, and the result-
ing element or compound is
reduced
.ThegasesH
2
(g),
N
2
(g), NH
3
(g), and CH
4
(g) are all reduced gases.
Table 1.4 shows structures of inorganic compounds
and methane, an organic compound, whereas Table 1.5
shows structures of additional organic compounds.
Inorganic compounds
are compounds that contain any
element, including hydrogen (H) or carbon (C), but not
both.
Organic compounds
are compounds that contain
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