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The periodic table
The periodic "law" of chemistry recognises that many properties of the chemical elements are periodic functions of their atomic number (the number of protons within the element's atomic nucleus).The element polonium is very much in the news at present, perhaps for the first time ever, and for the wrong reasons.This site does contain further information about polonium.The include Group 1 (alkali metals), Group 2 (alkaline earth metals), Group 15 (pnictogens, or pnicogens), Group 16 (chalcogens), Group 17 (halogens) and Group 18 (noble gases).Chancourtois, Lothar Meyer, and others.WebElements is rated as Best of the Web by Britannica.This page was last modified 09:34, 24 January 2008.The alkaline earth metals are a series of elements comprising Group 2 (IUPAC style) of the periodic table: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra).Mg(OH)2 + H2
Beryllium is an exception: It does not react with water or steam, and its halides are covalent.All the alkaline earth metals have two electrons in their outermost shell, so the energetically preferred state of achieving a filled electron shell is to lose two electrons to form doubly charged positive ions.Magnesium and calcium are ubiquitous and essential to all known living organisms.Strontium and barium have a lower availability in the biosphere.These elements have some uses in medicine, for example "barium meals" in radiographic imaging, whilst strontium compounds are employed in some toothpastes.Alkaline Earth Metals, Royal Chemistry Society.Science aid: Group 2 Metals Study aid for teens
Maguire, Michael E.All text is available under the terms of the GNU Free Documentation License.ABOUT THE ELEMENTS
There are only a few more than one hundred elements.The elements will be around
long after the letters of any alphabet are gone.It would serve
you well to know the elements.If you were to attempt to read
anything without knowing your letters, you would be in trouble.Your fluency in
reading would be ruined by having to look up the difference every
time you
encountered one of those letters.Some of
the symbols have one letter, some have two, but each element
symbol has one and only one upper case letter in it.Chemtutor has a Quickquiz to help you learn the names and symbols
of the elements.Latin, from which the element symbol was derived or
some other name that makes the element more
recognizable.You do not need to know the names in
parentheses.Aluminum is a
common metal to us.It is a good conductor of
electricity, particularly on consideration of its weight.Antimony is also used in flame proofing compounds and
in paints and pottery.It does not combine with other
elements.Argon is collected from the air by fractional
distillation.It has been known for centuries
that arsenic
compounds are poisonous.The least dense of the Group 2
elements, beryllium is a very hard, tough metal.Ores of
beryllium are not very plentiful.The element has been known for a
long time, but it was often confused with tin or lead centuries
ago.The organic compounds of
bromine are very important.Cadmium rods are used in control for atomic fission.It is an essential element
for
living things, especially in muscles, leaves, bones, teeth, and
shells.It is used in Portland
cement, mortar, plaster, and antacids.The element form of calcium, a soft metal,
was not known until the early in the nineteenth century by
electrolysis.Buckminster Fuller, the
predictor of such arrangements.Cesium is a Group 1 element used
in some photoelectric
cells and as a catalyst in organic reactions.Elemental chlorine is a greenish
dense gas that has been used in wartime as a poison gas.Chloride, the negative ion
of chlorine dissolved in water, is one of the common electrolytes
in living things.Elemental chlorine is released into water for
drinking or swimming to control bacterial and fungal growth.Chlorine is used in bleaches and organic compounds.Chromium is a metal element in many
ways resembling iron.It is used in alloys, often with iron, to
make harder metals and stainless alloys.It
is one of the best conductors of heat and electricity.Copper is about
the easiest metal to smelt.Fluorine is
the least dense, the smallest element number, of the halogen
group, Group 7 or 17.Fluorine is used in hydrofluoric acid to etch glass.The largest (highest element
number) Group 1 (alkali
metal) element, francium is radioactive.It is a natural decay product of actinium.By
extrapolation from the chart, Mendeleev predicted the properties
of Germanium.Germanium is used
the manufacture of semiconductors.Gold is the least active of the metals.The gold of the ancient
Incas buried many hundreds of years can be unearthed as shiny as
it was when new.Gold is
the most malleable material.It can be pounded into incredibly
thin sheets.The name helium refers to the sun
because it was first
detected in spectroscopic lines from sunlight.Helium is the
lightest of the noble gasses, Group 18.Helium is difficult to
acquire by fractional distillation of air because of its low
boiling
point, but it is available directly from the ground in helium
wells in Texas, USA.Almost all the hydrogen on earth is in the form of
compounds,
mostly water.Hydrogen is a diatomic gas as an element.With only one proton,
hydrogen has only one electron in a shell that can only contain
two electrons.There are many people working on the possibility of using hydrogen
as a fuel.The 'hydrogen economy' would require some changes in the
way we do things, but may be the only way we have as our petroleum
resources run out.Here are some references on the use of hydrogen as
a fuel.It dissolves in water only slightly, but in alcohol
fairly easily to make a purple solution.Iodine in alcohol
solution
is a commonly used antiseptic.Lack of iodine in human beings
causes an enlargement of the thyroid gland called goiter.As a gas it is a diatomic molecule.It
is usually not used as the pure element, but as the major
component
of a large number of alloys called steel.Carbon is one of the
elements added to iron to make various alloys.In general, the
more carbon in the mixture, the more brittle the iron alloy is.The carbon content of pig iron can be about three
percent.Other metals can be added to the iron to make
alloys with much improved properties, such as stainless steel.Krypton is an inert gas.If you
were a writer of fiction and wanted to describe a mineral with
unlikely properties, you might claim that the mineral would be a
compound of Krypton, since there are none.Lead is malleable and fairly soft.There is some argument that the Roman
upper classes having lead pipes and drinking mulled wine poisoned
themselves.Lead was commonly
used in making the pigments for house paint until the ninteen
fifties.As a metal
element it is as soft as cool butter.It burns in air to form the
oxide.It emits a beautiful crimson flame test.It is used mainly in
steel alloys to harden them.It has a regular coefficient of expansion, so the
most likely place for you to have seen elemental mercury is in a
liquid thermometer.As a liquid conductor of electricity, mercury
is used as the switch in thermostats.Mercury makes alloys called
amalgams with many metals.For many years amalgams have
been used as fillings for teeth.Liquid mercury has a fairly high vapor
pressure, and the gas from it is a cumulative poison.Nitrogen gas is a diatomic molecule with a triple (covalent) bond
between the atoms.The strong bond makes the element
somewhat inert.Since many organic compounds require nitrogen,
its availability is a limiting factor on biological growth.Thus,
nitrogen compounds are included in many fertilizers.This is a part of the
intriguing story of how chemistry and history and farming and
ecology are all intertwined with the nitrogen cycle.Just as nitrogen, oxygen is
abundantly available in
element form in the atmosphere.Pure oxygen at atmospheric pressures can fully
ignite a glowing wood splint, this being the classic test for the
presence of oxygen.Phosphates in
waste water pumped directly into streams will produce a
proliferation of algae that clog waterways.C, just thirty degrees below
the boiling point, and cooling.Red phosphorus does not
spontaneously ignite in air and is not poisonous as is the white
or yellow phosphorus.The free element platinum is a
metal almost as inactive as gold.Finely divided platinum
can serve as a catalyst for several reactions.The word potash refers to
potassium.That name may
have come from the practice of leaching potassium (and
sodium) hydroxide from the ashes of burnt wood.The lye
(hydroxides) would be boiled with fat (from meats cooked on
that same fire) to make soap.The
tarnishing can be slowed by storing the metal under kerosene.Potassium is a Group 1 element, an alkali metal.Potassium ions are not only not poisonous, but they are required
by living things.Potassium
chloride is often used as a table salt substitute for people who
wish to limit the sodium intake.Radium is the element that first
made Madam Curie
famous.She and a coworker were the first to isolate the
element.The radiation from radon has been shown to cause cancer
in human beings in some buildings in which the radon seeps in
from cracks in basement floors.Chemically silicon is
similar to carbon.Silicones, organic compounds with silicon in placed of
carbon, have been used to for an incredible number of biological
tasks.Silver is
the best of conductors of heat and electricity and almost the
most malleable and ductile metal, second only to gold.The black
tarnish on silver is silver sulfide, usually from combination
with
sulfur compounds in the air.Sodium chloride, table salt, is its most common
compound.Soda lye, or caustic soda, is sodium
hydroxide.The flame test for strontium
is a brilliant dark red.Elemental strontium is a hard silvery metal of
Group 2, very similar to calcium.Strontium 90, a radioactive
isotope of strontium, can be in the fallout from nuclear
explosions.It has been recorded that strontium 90 landing on
vegetation eaten by dairy cattle can appear in the milk of those
animals, similarly the usual calcium.Under
pressure, as under the earth, water temperature can exceed the
melting temperature for sulfur.Superheated water
under pressure is pumped into the earth and retrieved with melted
sulfur in it, mimicking the natural process for sulfur exposure.Sulfur burns in air (the stone that burns) to form
sulfur dioxide.This is the first step in the manufacture of
sulfuric acid, by far the most used compound of sulfur.It has
been said that the amount of sulfuric acid made is a good measure
of the level of industrialization of a country.Tin was the secret ingredient in
bronze that made it
possible for the copper alloy to hold a minimal edge for swords.Tin is a
metal element that has a characteristic tendency to form crystals
in the solid metal.Pewter and solder
are other important alloys of tin.Titanium is much stronger
per mass than iron.Airplanes, bicycles, and ultracentrifuge
rotors are some of the items that work best made of titanium
because of its lightness (small density) and great tensile
strength.Having a melting point of almost
six thousand
degrees Celsius and good electrical conductivity, Tungsten makes
a good light bulb filament.The
great majority of tungsten is used to alloy with steel to make a
hard, tough metal for uses like high speed drilling and cutting
tools.The highest atomic number of the
naturally occurring elements, uranium has a fissionable isotope.Some nuclear energy facilities use uranium as the
fuel to make electricity.The heaviest and the rarest of the
naturally occurring
inert gases in air, xenon produces a beautiful blue glow in
fluorescent tubes.As the other inert gases, it
makes no natural compounds.For many centuries zinc was included
in the metals of
brass without being recognized as an element.Zinc oxide is used
as an antiseptic and as a white pigment.Under the same exception granted to classroom teachers, full
recognition of Chemtutor must be given when all or any part is included in
any other electronic representation, such as a web site, whether by direct
inclusion or by hyperlink.Its beauty lies in its logical development of geometry and other branches of
mathematics.It has influenced all branches of science but none so much as mathematics and the exact
sciences.The Elements have been studied 24 centuries in many languages starting, of course,
in the original Greek, then in Arabic, Latin, and many modern languages.I'm creating this version of Euclid's Elements for a couple of reasons.The main one is to
rekindle an interest in the Elements, and the web is a great way to do that.Another reason
is to show how Java applets can be used to illustrate geometry.That also helps to bring the
Elements alive.If you enable Java on your browser, then you'll be able to dynamically
change the diagrams.This is a major problem because
deductive logic is learned almost exclusively in geometry.Modern mathematics and science use deductive logic as a primary tool of understanding.For a broader criticism of mathematics education in the United States,
see the site Mathematically Correct.
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