CHEMISTRY OF HYDROGEN, OXYGEN, NITROGEN, AND
CARBON
I. Descriptive chemistry is the systematic examination of
the elements and the compounds they form.
II. Periodic Trends
A. Periodic trends are trends in properties that
correlate to an element's position in the periodic
table.
1. Electronegativity is a measure of an element's
ability to compete for electrons in a bond.
In general, nonmetals have higher electronegativities
than do metals.
2. Compounds formed between strongly metallic and
strongly nonmetallic elements tend to be ionic.
Compounds formed between nonmetals are molecular
substances.
B. Among the nonmetals, the first member of each group
often differs in several important ways from subsequent
members. These differences are due, in large part, to
the smaller size and higher electronegativity of the
first member.
1. The first member is restricted to forming a
maximum of four bonds because it has only the 2s
and the three 2p orbitals available for bonding.
2. The first member has a greater ability to form pibonds than do subsequent members.
III. Chemical Reactions
A. In complete combustion, the element being oxidized
with O2 is taken to its highest oxidation state.
B. Bronsted acid-base (proton-transfer), metathesis
(double-displacement), single displacement, and redox
reactions are also discussed.
IV. Hydrogen
A. Hydrogen is the most abundant element in the
universe. There are three isotopes: protium (no
neutrons), deuterium (one neutron), and tritium (two
neutrons).
B. Hydrogen is the only element that is not a member of
a family in the periodic table. Hydrogen forms both
a cation, H+, and an anion, H-. The properties,
preparation, and uses of hydrogen are given.
C. Hydrogen forms three different types of hydrides.
1. Ionic hydrides are formed between hydrogen and the
alkali metals and alkaline earth metals.
2. Metallic hydrides are formed between hydrogen and
transition metals. The metallic properties of the
metal are preserved in the hydride.
3. Molecular hydrides are formed between hydrogen and
nonmetals or semimetals.
D. "Chemistry at Work: Using Metal Hydrides" examines
research for using hydrides as storage media for H2.
Discussion Question: Why is hydrogen so abundant in the universe
but so comparatively uncommon on earth?
V. Oxygen
A. Oxygen is the most abundant element in the earth's
crust and in the human body. Oxygen occurs in two
allotropes, molecular oxygen O2 and ozone O3. The
properties, preparation, and uses of oxygen, O2, are
given.
B. Ozone was discussed in detail.
C. Oxides are oxygen-containing binary compounds in
which oxygen is in the -2 oxidation state.
1. Acidic anhydrides or acidic oxides contain a
nonmetal combined with the oxygen.
2. Basic anhydrides or basic oxides contain a metal
combined with oxygen.
3. Amphoteric oxides can exhibit either acidic or
basic character.
D. Peroxides contain an -O-O- unit with each oxygen in a
-1 oxidation state. Superoxides contain an -O-O-unit
with each oxygen in a -1/2 oxidation state.
E. The oxygen cycle is a term applied to oxygen's
repetitive collection, use, and return to the
environment.
Discussion Question:
Why might hydrogen peroxide burn your skin?
VI. Nitrogen
A. The properties, preparation, and uses of nitrogen,
N2, are given.
B. Ammonia can be produced in the laboratory by the
action of NaOH with NH4Cl. Commercially, ammonia is
produced by the Haber process.
C. Nitrogen forms three common oxides and two common
oxyacids. The properties, preparations, and uses of
these compounds are given.
1. Nitrous oxide (N2O), nitric oxide (NO), and
nitrogen dioxide (NO2) are the three oxides.
Nitrogen dioxide dimerizes at low temperature,
yielding N2O4.
2. Nitric acid, HNO3, is a strong oxidizing agent and
is produced by the Ostwald process. Nitrous acid,
HNO2, is a weak acid.
D. Nitrogen has a cycle of use and regeneration in
nature called the nitrogen cycle.
VII. Carbon
A. We often refer to compounds of carbon that have no
C-H bonds as inorganic carbon.
B. Carbon exists in several elemental forms: graphite,
diamond, carbon black, charcoal, and coal.
C. "Chemistry at Work: Carbon Fibers and Composites"
shows how carbon is used in structural materials.
D. There are two oxides of carbon and several compounds
based on the carbonate ion, CO32-.
1. The environmental hazards of CO were discussed. CO is
a good reducing agent.
2. Carbon dioxide is produced when carbon-based fuels
are burned in excess oxygen and when carbonates
are heated or treated with acid.
E. The only oxyacid of carbon is carbonic acid, H2CO3, which
results from dissolving CO2 in water. Carbonate
minerals are very common, particularly calcite or common
limestone, CaCO3.
F. Binary compounds of carbon with metals, semimetals,
and certain nonmetals are called carbides.
1. Ionic carbides or acetylides, C22-, are formed
with electropositive metals.
2. Interstitial carbides are formed with transition
metals.
3. Covalent carbides are formed with boron and
silicon.
Discussion Question: Which element, C, O, or H, seems to be the
most important element and why?
SAMPLE QUIZ QUESTIONS
1. What are the components of water gas, an important
industrial fuel?
2. What is meant by the term
interstitial hydride?
3. Different forms of the same element in the same physical
state, such as O2 and O3, are known as _________________.
4. Write balanced chemical equations for the following
reactions: (a) Sodium oxide is dissolved in water;
(b) Calcium hydride is dissolved in water; (c) Sodium
peroxide is dissolved in water; (d) KClO3(s) is heated; (e)
CaCO3(s) + H+(aq) -->; (f) Zinc metal reacts with sulfuric
acid.
5. Give the chemical formula for: (a) hydrazine; (b) ozone;
(c) calcium carbide.
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6. List two general ways that the first member of a periodic
family differs from subsequent members.
7. Describe, using chemical equations, the preparation of
nitric acid, starting with N2, H2, O2, and water.
8. Classify the oxides from the following elements or groups
as acidic, basic, or amphoteric: (a) Al; (b) alkali metals;
(c) halogens; (d) Ba; (e) S.
9. Give the name and formula of a compound that contains the:
(a) peroxide ion; (b) superoxide ion; (c) hydride ion.
10. List one commercially important reaction of each of the
following: (a) H2; (b) NH3; (c) CaC2.
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