ELEMENTS and COMPOUNDS
1.01 The ancient Greeks thought that everything was made up in varying proportions
of four things: earth, fire, air and water. Today we believe that here on earth, and probably
in the other planets, and suns there are 90 naturally occurring elementary materials or
and everything is either an element, or composed of different elements in certain
(not arbitrary proportions). Such combinations are
More about them
a bit later after introducing atoms and molecules.
The point is then that every thing is either an element or a compound, or as in the
human body a mixture
of elements and thousands of different compounds.
METALS, NON-METALS and their SYMBOLS
1.02 You are very familiar with many elements directly, and with the names of many
more. We have found it convenient to classify elements as either
METALS or not metals,
We list some of the more important
ones (for our purposes ) below. We
also append the chemical symbol for them. The SYMBOL
1.03 The symbol for am element is one or two letters. It is just a
shorthand way of writing the name of an element. For materials known for centuries the name is often
the Latin name.
We sometimes added a word to jog your memory or make a
Table 1.1 Some Common Metals and Nonmetals
Copper Cu (cuprum)
Iron Fe (ferrum)
Tin Sn (stannum)
Silver Ag (argentum, Argentina)
Mercury Hg (hydragyrum-silver water)
gold Au (aurum)
Lead Pb (plumbum-plumber)
Sulfur S (sulphur- Yellowstone)
Carbon C (charcoal, soot, diamond)
The following metals are so active,
they combine so readily with the oxygen
and water of the environment,
their compounds are found.
Sodium Na (Natrium-soda, hyponatremia)
Potassium K (Kalium-potash, hypokalemia)
The following non-metals are gases
at normal environmental conditions.
They can be cooled to very low temperatures
and compressed into very cold liquids
Oxygen O (colorless, odorless, comprises 21%
of the air)
Nitrogen N (colorless, odorless,
Comprises 78% of the air)
Chlorine Cl (pale greenish-yellow gas
has the odor of Chlorine bleach. So very active that only its
compounds are found on earth.)
Hydrogen H (So very light, that
if produced it escapes
into outer space)
The MOLE-- a Unit of Counting
2.01 Atoms are the smallest part of matter capable of an independent existence.
of the same element have the same weight and size. Atoms of different elements, differ in
size and weight.
So how big is an atom? Very roughly, one would have to line up a
( that is a million taken a thousand times) atoms for the line to be one inch long.
Molecules are collection of atoms which we find convenient to consider
as a unit. Many molecules contain only two or three atoms. Other molecules contain
hundreds of thousands of atoms. Examples of these macromolecules are enzymes. DNA,
Since individual atoms are so very small and therefore weigh such a slight amount,
how does one handle them? In large groups. Just as one might count oranges and eggs by
the dozens, or gross, so the chemist has a special unit for counting these small objects. It is
called the mole (abbv. Mol) There are twelve items in a dozen, twelve times twelve
items in a gross. There are six hundred thousand times a billion times a billion items in a
ATOMIC and MOLECULAR WEIGHTS
Why is a mole such an odd number? Because of the weight of the lightest
known-- hydrogen. A mole of hydrogen atoms weigh one gram. A carbon atom weighs
twelve times as much as a hydrogen atom, and so a mole of carbon atoms weigh 12 grams.
An oxygen atom is sixteen times as heavy as a hydrogen atom, and therefore a mole of
oxygen atoms weigh 16 grams.
2.04 The weight of a molecule is nothing but the sum of the weights of the atoms that
make it up. Since the oxygen gas that we breath is a molecule consisting of two oxygen
atoms bound together O2, a mole of oxygen
molecules weigh 32 grams. Similarly, water
has two hydrogen atoms bound to an oxygen atom,
H2O, and a mole of water molecules
has a molecular weight of 18 grams.
THE PERIODIC CHART OF THE ELEMENTS
3.01 Compounds are molecules that contain two or more different atoms. They are not
mixtures. The proportions of mixtures can be varied. The composition of a compound is
fixed. Water has two hydrogen atoms tied to an oxygen atom, H2O Hydrogen peroxide,
“peroxide” bleach, has two hydrogen atoms tied to two oxygen atoms,
As with elements, we find it convent to classify compounds into two groups.
Compounds can be either organic compounds, or not-organic, that is inorganic
Organic compounds were so named because they were thought at one time to be
exclusively associated with organized, that is living, matter.Today
we recognize that organic molecules are compounds of carbon and hydrogen. They may contain
other non-metals, principally oxygen, nitrogen, phosphorous and sulfur.
Inorganic materials were the
dead rocks, water, air of our environment. In Table 3.1 below we cite some very familiar
Table 3.1 Some Common Organic and Inorganic Materials
Methane (natural gas)
propane (LPG gas)
Salt (Sodium Chloride)
Carbon Dioxide (dry ice)
3.02 The word Valence
in chemistry means Combining Power or Joining Power. Atoms can have a
single valence, or in a few cases multiple valences.
with two or more atoms
together the atoms are said to be joined by a
Hydrogen has a valence of one, oxygen a
valence of two. Hence in the water molecule, two hydrogens are bound
to a single oxygen atom.
Organic Compounds are Covalent Compounds with carbon having a
covalence of four, hydrogen one, oxygen two and nitrogen three.
4.01 We are all familiar with static electricity--
static on an AM radio station, lightning
discharges, static cling and so forth. In the cold winter states one can build up a “static charge” by
sliding across plastic car seats. A spark jumps then when you touch the metal door handle.
For thousands of years we have recognized two types of electricity.
Vitreous (glass-like) and resinous (amber). The ancient Greeks called
amber, electra. Amber is the fossilized sap of pine trees. It takes a
high polish, and after rubbing it, a spark can jump to a piece of metal.
Benjamin Franklin, of flying-kites-in-
thunderstorm-fame, named vitreous electricity--positive; resinous
Usually matter is electrostatically
neutral; it contains equal parts of positive and negative
ELECTRICAL NATURE OF ATOMS
4.03 We believe that all atoms have a positively
charged nucleus, and surrounding the nucleus like planets orbiting the sun, are
electrostatically negatively charge particles called electrons.
The nucleus of an atom contains a certain
number of positively charged particles called protons. Outside the nucleus are
the same number of negatively charged electrons.
All the atoms a certain element have the
same number of positive protons in their nuclei. This is what makes the element
what it is. All iron atoms have 56 protons in their
nuclei; hydrogen atoms have one proton in their nuclei; carbon
atoms 6 protons in their nuclei. Outside the nuclei the orbiting electrons are
equal in number to the number of protons in the nuclei.
THE ELECTRONIC SHELL STRUCTURE OF ATOMS
The word Valance in chemistry means Combining Power. Atoms can have a single
valance, or in some cases multiple valences. If atoms combine to form compounds by
sharing their electrons, we say they are COVALENT COMPOUNDS.
The covalence of some common Non-metallic elements are listed below
Non-metals combining with non-metals form covalent compounds
Most Organic Compounds are Covalent Compounds
Element Covalence Examples
Hydrogen 1 H2
Carbon 4 CH4 methane
Oxygen 2 O2 normal oxygen; H2O water
Nitrogen 3, 5 NH3 ammonia
Sulfur 2, 4 or 6 H2S hydrogen sulfide
SO2 (4-valent sulfur) sulfur dioxide
SO3 (6-valent sulfur) sulfur trioxide
Generally, when metals combine with non-metals, they form ionic compounds.
In this instance, the metal atoms lose a number of negative electrons forming positive
ions (cations). The non-metals atoms gain the negative electrons and form negative ions
(anions). There is still overall electrical neutrality since just as many electrons are lost by
the metals as are gained by the non-metals.
Sometimes covalent molecules composed of several non-metallic atoms gain or
lose electrons as a whole. These are then called molecule-ions, or radicals. The ionic
valences of several elements and molecular-ions are given below.
ION or RADICAL
Sodium ion Na+1 Chloride ion C l -1
Potassium ion K+1 Fluoride ion F-1
Calcium ion Ca+2 Sulfide ion (S-2)
Hydrogen ion H+1 Sulfite ion (SO3)-2
******************* Sulfate ion (SO4)-2
Magnesium ion Mg+2 Carbonate ion (CO3)-2
Iron ferrous ion Fe+2 Bicarbonate ion (HCO3)-1
Iron ferric ion Fe+3 Nitrite ion (NO2)-1
Ammonium ion NH4+1 Nitrate ion (NO3)-1
Hydroxide ion (OH)-1
Oxide ion O-2
You notice that we have the non-metal hydrogen forming a positive ion,
and the non-metallic molecule ammonia adding a positive hydrogen ion to form the
non-metallic positive radical: ammonium ion . All attempts to make the neutral compound
ammonium (NH4) have failed.
HYDROCARBONS and RELATED MATERIALS
As the name implies, hydrocarbons are compounds of carbon and hydrogen. Their
principle source by far is petroleum, natural gas and petroleum tars. There are hundreds of
distinct but related hydrocarbons.
Methane, CH4, is the principle constituent of natural gas, it is also
produced in the intestinal tract of animals. It itself is odorless.
Ethane, C2H6 , is also a constituent of natural gas
Propane, C3H6 and Butane, C4H10 similarly are separated from natural gas
or from petroleum. They are easily liquefied and sold as LPG (liquefied petroleum gas).
Remember that hydrogen always has a valance of one, carbon of four. So there are always
four bonds coming out of a carbon atom. We show the formulas for the hydrocarbons just
mentioned as line-formulas.
H H H H H H H H H H
H-C-H H-C-C-H H-C-C-C-H H-C-C-C-C-H
H H H H H H H H H H
CH4 C2H6 C3H8 C4H10
These hydrocarbons are said to be saturated ; the carbon atoms are attached to as
many hydrogen atoms as possible. We call them straight chain hydrocarbons because of
the way we write the formulas. In reality they twist around in three dimensions, so that in
a six carbon chain, the sixth and first carbon atoms are near each other. Baby Oil,
petroleum jelly, Vaseline are purified mixtures of straight chain hydrocarbons with12 to 20
carbon atoms in the chain.
Structural Formulas of Organic Compounds
Isomers, (not isotopes) are what give rise to the tremendous diversity of organic
Acids, Bases and Salts
These are very generic terms and over the years their
definitions have expanded to cover many materials not
thought to be so a hundred years ago.
For our purposes an acid is a material which increases the hydrogen ion
concentration of a water solution. This water solution includes blood and any biological
For instance, hydrogen chloride (HCl) is a good covalent gaseous compound. When
dissolved in water it ionizes completely into positive hydrogen ions and negative chloride
ions. We call this mixture hydrochloric acid. It is to be emphasized that the hydrogen
ions (H+) and the chloride ions (Cl-) move about independently of one another. It is said
that the concentration of the digestive juice “hydrochloric acid “in the stomach is about
0.1 mol per liter. (3.6 g per liter) But here, the chloride ion comes from the salt NaCl in
our food, and the hydrogen ion is secreted by cells in the stomach wall.
An acid that ionizes completely in a water solution, such as hydrogen chloride , is called a
strong acid. This has nothing to do with how concentrated the acid solution is.
Again, for our purposes there are about three strong acids, Hydrochloric Acid HCl,
Sulfuric Acid H2SO4, and Nitric Acid HNO3
Further, the useful, sometimes dangerous, property of there materials is often not their
“Acid” property. Concentrated sulfuric acid is a very strong dehydrating agent. Nitric acid
is a very powerful “oxidizing agent”
Essentially any other acid is a weak acid. That is, only a very small fraction of the acid
molecules present in fact ionize into a hydrogen ion and a negative ion. In vinegar, which
legally must contain at least 6% acetic acid, only about 0.01% of the molecules ionize.
You are familiar with the names of many acids. acetic acid (vinegar), carbonic acid
(carbonated beverages), citric acid (citrus fruits),
Some acids we will be considering further are given in Table XX
HCl hydrochloric Acid
H2SO4 sulfuric acid
HNO3 nitric acid
Sulfurous acid H2SO3
Carbonic acid H2CO3 bicarbonate ion HCO3-
Phosphoric acid H3PO4
Dihydrogen phosphate ion H2PO4-
monohydrogen phosphate ion HPO4-2
A BASE is a material that when combined with an acid, forms a salt. That is it’s the basis
for making a salt. Commonly recognized bases are the oxide ion,(O-2) and the more
common hydroxide ion (OH-) in the Table below we list some common oxygen based
bases. : You will note that some of the materials listed previously as acids, have a dual
nature ;they can also function as bases
Oxide, hydroxide, carbonate, hydrogen carbonate , phosphate, monohydrogen phosphate,
In nature these materials that are ionic must be found with a positive counter ion, usually,
sodium, potassium, calcium, magnesium,
Some specific examples are
Sodium carbonate (washing soda) High concentrations found in some African lakes.
An aqueous solution will have a pH ~10. Very Caustic
Sodium bicarbonate (baking soda, alka selzer) aqueous solution pH~7.
In any water solution, H2O ; HOH, there is a balance between the concentration of
hydrogen ions H+ and the concentration of hydroxide ions OH-.In (acid/base) neutral
water the two concentrations are equal If the solution becomes more acidic, hydrogen
ions increase, then there is a corresponding decrease in the hydroxide ion concentration.
Contrawise if the hydrogen ion concentration of a water solution drops below that of
“pure” water, the hydroxide ion concentration increases--- the solution becomes more
basic, or more alkaline.
pH is a measure of the hydrogen ion concentration. The pH numbers work in a backwards
fashion As the concentration of hydrogen ion increases, the pH number decreases.! In
neutral “pure” water the pH has a value of 7. Because of the digestive acids in the
stomach, it’s fluid has a pH of about 1. very acidic. The pH of the upper intestines is about
8, somewhat basic. Carbonated beverages have a pH of about 5. The blood’s pH shouldn’t
vary much from the value of 6.7, slightly acidic.
Acid Base Buffers
This value of pH=6.7 of the blood is maintained by two buffer systems . The first system is
the bicarbonate---carbonic acid system . If the hydrogen ion concentration starts to rise,
(the pH drops) say from eating too much sauerkraut, the excess hydrogen ions react with
the bicarbonate ions to produce covalent carbonic acid. This decomposes in the lungs into
water and carbon dioxide CO2, which is exhaled.
Essentially every biochemical reaction in the body is mitigated, catalyzed, by an enzyme.
These enzymes work only in very restricted pH ranges. Hence the need to maintain the
proper pH in various parts of the body.
Organic derivatives of the simple compound ammonia, NH3 form a very large class of .
nitrogenous bases . We mention most of them latter. Here let us remind you that pyrrole,
the foundation of heme, is a nitrogen containing base.
When a hydrogen ion is added to the base ammonia NH3 one forms the ammonium ion.
Alkaloids are nitrogenous bases of a plant origin, which have a physiological action. One
needs mention only caffeine, codeine, cocaine, morphine, nicotine.
The DNA code is comprised of four (nitrogenous) bases.
Too simply, a salt may be defined as the product of an acid and a base combining
chemically. The base supplies the positive ions of the salt; the acid provides the negative
ions. Alternately then, one can consider a salt as a metal--- non.metal ionic combination.
Here we must remember that nitrogenous bases can function as a metal ion.
We list here many common salts and indicate a chemical reaction whereby they might be
Sodium chloride: NaOH + HCl >>> H2O + NaCl
Potassium Chloride K2CO3 +2 HCl>>>H20 + CO2 + 2 KCl
Sodium sulfate Na2CO3 + H2SO4>>> H2O + CO2 + Na2SO4
Calcium Sulfate CaCO3 + H2SO4>>> H2O + CO2 + CaSO4
Sodium Chloride and Sodium Sulfate are commonly the principle constituents of
the “alkali” in alkali land, alkali wells.
Calcium Sulfate is common as the mineral gypsum, and in the building product
Magnesium Sulfate is Epsom Salts.
The Barium ion is highly toxic. But Barium Sulfate is highly insoluble in the body
fluids. Hence one can take “Barium enemas” and “Barium cocktails “with relative safety
since what one is taking is a thick suspension of barium sulfate
. I know of no “SULFATE” (or sulphate) that is harmful to people because of the
”sulfate“ part of the compound.
Silver nitrate is one of the few silver compounds that are water soluble. It is used
medically to cauterize bleeding wounds.. The active agent is the silver ion, not the nitrate
ion. An old fashioned name for silver nitrate is ” luna caustic” since the alchemists symbol
for silver was the moon; and it burns, cauterizes wounds.
Potassium nitrate, saltpeter, finely mixed with sulfur and charcoal form “Black
Gunpowder” In the nineteenth century saltpeter or “ nitre“ deposits were much sought, to
maintain the European wars and in hunting and warfare in the America .
Sodium nitrate, Chile saltpeter, is found in the Desert of Chile. It was mined for
use as a nitrate fertilizer. IT IS UNSUITABLE FOR THE MAKING OF GOOD
QUALITY BLACK GUNPOWDER.
Ammonium Nitrate. Is manufactured, and use as a fertilizer and as an explosive.
Sodium , carbonate, bicarbonate
Phosphate Salts, apatite, hydroxyapetite, fluoroapetite.
milk of magnesia
4.04 Just to complicate this simple situation
of an atom can contain a certain number of neutral particles called
neutrons.. The number of these electrostatically neutral
particles can vary somewhat. Isotopes
of an element have the same
number of protons and electrons, but different number of neutrons. Most carbon
atoms (C12) have six protons and six neutrons. About 1.3% of the naturally
occurring carbon (C13) has 6 protons and 7
neutrons. The radioactive carbon atoms (C14) have 8 neutrons in their nuclei.