Transcript elements 18 - Junction Hill C

• Hydrogen is the lightest
element. It is by far the
most abundant element in
the universe and makes up
about about 90% of the
universe by weight.
Hydrogen as water (H2O)
is absolutely essential to
life and it is present in all
organic compounds.
Hydrogen gas was used in
lighter-than-air balloons for
transport but is far too
dangerous because of the
fire risk (Hindenburg).
• Lithium is a solid only
about half as dense as
water. A freshly cut chunk
of lithium is silvery, but
tarnishes in a minute or so
in air to give a gray
surface.
• Lithium is mixed (alloyed)
with aluminum and
magnesium for light-weight
alloys, and is also used in
batteries, some greases,
some glasses, and in
medicine.
• Pure aluminum is a silverywhite metal with many
desirable characteristics. It
is light, nontoxic and
nonmagnetic It is easily
formed, machined, and cast.
Pure aluminum is soft and
lacks strength, but alloys
with small amounts of
copper, magnesium, silicon,
manganese, and other
elements have very useful
properties. Aluminum is an
abundant element in the
earth's crust, but it is not
found free in nature.
Carbon is found free in nature in
different forms. Two forms in takes
are graphite and diamond. Graphite is
one of the softest known materials
while diamond is one of the hardest.
Carbon is found in some meteorites.
Natural diamonds are found in
ancient volcanic "pipes" such as
found in South Africa. Carbon is
present as carbon dioxide in the
atmosphere and dissolved in all
natural waters. It is a component of
rocks as limestone. Coal, petroleum,
and natural gas are chiefly
hydrocarbons. Carbon is unique
among the elements in the vast
number of variety of compounds it
can form.
Sulfur is found in meteorites,
volcanoes, hot springs, and as
galena, gypsum, Epsom salts,
and barite. It is recovered
commercially from "salt
domes" along the Gulf Coast
of the USA. Jupiter's moon Io
owes its colors to various
forms of sulfur.
Sulfur is a pale yellow,
odorless, brittle solid, which
is insoluble in water but
soluble in carbon disulphide.
Sulfur is essential to life. It is
a minor constituent of fats,
body fluids, and skeletal
minerals.
About one fifth of the atmosphere is
oxygen gas. Oxygen is the third most
abundant element found in the sun.
Oxygen in excited states is responsible
for the bright red and yellow-green colors
of the aurora. About two thirds of the
human body, and nine tenths of water, is
oxygen. The gas is colorless, odorless,
and tasteless. Liquid and solid oxygen are
pale blue.
Ozone (O3) is a form of oxygen. It is
formed from electrical discharges or
ultraviolet light acting on O2. It is an
important component of the atmosphere
which is vital in preventing harmful
ultraviolet rays of the sun from reaching
the earth's surface. Oxygen is very
reactive It is essential for respiration
of all plants and animals and for most
types of combustion.
Copper is one of the most
important metals. Copper is
reddish with a bright metallic
luster. It is malleable, ductile,
and a good conductor of heat
and electricity (second only
to silver in electrical
conductivity). Its alloys, brass
and bronze, are very
important. Gun metals also
contain copper. Apparently
the reason that policemen are
nicknamed "cops" or
"coppers" is to do with their
uniforms which used to have
copper buttons.
Chlorine is a greenish
yellow gas which combines
directly with nearly all
elements. Chlorine is a
respiratory irritant. The gas
irritates the mucous
membranes and the liquid
burns the skin. As little as
1000 ppm is likely to be
fatal after a few deep
breaths. It was used as a
war gas in 1915. It is not
found in a free state in
nature, but is found
commonly as NaCl (solid
or seawater).
The metal is the seventh most
abundant and makes up about 1.5 % by
weight of the earth's crust. Potassium
is an essential constituent for plant
growth and it is found in most soils. It
is also a vital element in the human
diet.
Potassium is never found free in
nature. It is one of the most reactive
metals and, apart from lithium, it is the
least dense known metal. It is soft and
easily cut with a knife. It is silvery in
appearance
It oxidizes very rapidly in air and must
be stored in mineral oil. It usually
catches fire during the reaction with
water.
Mercury is the only
common metal liquid at
ordinary temperatures.
Mercury is sometimes
called quicksilver. It rarely
occurs free in nature. It is
a heavy, silvery-white
liquid metal. It is a rather
poor conductor of heat as
compared with other
metals but is a fair
conductor of electricity. It
alloys easily with many
metals, such as gold,
silver, and tin.
Ordinary tin is a silverywhite metal, is
malleable, somewhat
ductile, and has a highly
crystalline structure.
Tin resists distilled, sea,
and soft tap water, but is
attacked by strong acids.
Oxygen accelerates the
attack. It is, or was, used
to plate steel, making
"tin cans". Tin is used as
one component in bell
metals.
Calcium is a metallic
element, fifth in abundance
in the earth's crust. It is an
essential constituent of
leaves, bones, teeth, and
shells.
The metal is a silvery color
and is rather hard. It readily
forms a white coating in
air, reacts with water, burns
with a yellow-red flame.
Calcium does not occur
free in nature. Calcium is
found mostly as limestone,
gypsum and fluorite.
Stalagmites and stalactites
contain calcium carbonate.
Nitrogen makes up about 78% of the
atmosphere by volume but the
atmosphere of Mars contains less than
3% nitrogen. Its compounds are vital
components of foods, fertilizers, and
explosives. Nitrogen gas is colorless,
odorless, and generally inert. As a
liquid it is also colorless and odorless.
When nitrogen is heated, it combines
directly with magnesium, lithium, or
calcium. When heated under pressure
with hydrogen in the presence of a
suitable catalyst , ammonia forms
Nitrogen is "fixed" from the
atmosphere by bacteria in the roots of
certain plants such as clover. Hence the
usefulness of clover in crop rotation.
Lead is a bluish-white lustrous
metal. It is very soft, highly
malleable, ductile, and a
relatively poor conductor of
electricity. It is very resistant to
corrosion but tarnishes upon
exposure to air. Lead pipes
bearing the insignia of Roman
emperors, used as drains from
the baths, are still in service.
Alloys include pewter and
solder. Tetraethyl lead is still
used in some grades of gasoline
but is being phased out on
environmental grounds.
Iron is a relatively abundant element
in the universe. It is found in the sun
and many types of stars in
considerable quantity. Iron is a vital
constituent of plant and animal life,
and is the key component of
hemoglobin.
The pure metal is not often found in
pure form, but is usually alloyed with
carbon or other metals. The pure
metal is very reactive chemically,
and rapidly corrodes, especially in
moist air or at elevated temperatures.
Any car owner knows this. Iron
metal is a silvery, lustrous metal
which has important magnetic
properties
Sodium is a silvery white
metal. Sodium would
not normally be made in
the laboratory as it is so
readily available
commercially.
Sodium is present as salt
(sodium chloride, NaCl)
in huge quantities in
underground deposits
(salt mines) and seawater
and other natural waters.
It is easily recovered as a
solid by drying.
Magnesium is the eighth
most abundant element in
the earth's crust although
not found in it's elemental
form.
Magnesium tarnishes
slightly in air, and finely
divided magnesium readily
ignites upon heating in air
and burns with a dazzling
white flame. Normally
magnesium is coated with a
layer of oxide, MgO, that
protects magnesium from
air and water.
Silver is somewhat rare and
expensive, although not as
expensive as gold. Slag dumps in
Asia Minor and on islands in the
Aegean Sea indicate that man
learned to separate silver from lead
as early as 3000 B.C. Pure silver
has a brilliant white metallic luster.
It is a little harder than gold and is
very ductile and malleable. Pure
silver has the highest electrical and
thermal conductivity of all metals.
Silver iodide, AgI, is (or was?)
used for causing clouds to produce
rain.
Silver is stable in pure air and
water. It occurs in ores including
argentite, lead, lead-zinc, copper
and gold found in Mexico, Peru,
and the USA.