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WEEK 3
CHEMICAL SHORTHAND: SYMBOLS, FORMULAS, AND EQUATIONS
There are 88 elements which naturally occur in our surrounding environment. Of these
only about 24 will be routinely used in chemical interactions. The symbols for these
elements appear in two forms: one-letter symbols that are always expressed as a single
capital letter, and two-letter symbols that always contain one capital letter and one lowercase letter. SYMBOLS are abbreviations for the element. The trick is to be able to
distinguish among elements whose symbols start with the same letter. For example,
copper, calcium, carbon and chlorine all have symbols that begin with C. Some symbols
bear little resemblance to their elements name. This is usually because the symbol came
from the Greek or Latin root of the word. For example: the symbol for iron is Fe. The
Fe comes from the Latin word for iron, Ferrum.
A symbol represents:
1. The name of the element
2. One atom of the element
3. The atomic weight of the element
The following is a list of elements and their symbols:
Element name
Aluminum
Bromine
Calcium
Carbon
Chlorine
Copper
Fluorine
Helium
Hydrogen
Iodine
Iron
Mercury
Nitrogen
Oxygen
Phosphorus
Potassium
Sodium
Sulfur
Symbol
Al
Br
Ca
C
Cl
Cu
F
He
H
I
Fe
Hg
N
O
P
K
Na
S
FORMULAS – Compounds have been defined as two or more elements chemically
combined in a definite proportion by weight. The two or more elements that comprise a
compound are called “constituents” of that compound and usually involve a metallic
portion and a non-metallic portion. Metallic elements generally have a positive oxidation
number and are written first in the formula. Non-metallic elements generally have a
negative oxidation number and are written last in the formula. FORMULAS represent
the abbreviation for a compound (just as a symbol is an abbreviation for an element).
The definition of a formula is a combination of symbols used to express the chemical
composition of a substance.
The object of formula writing is to achieve an inert-gas configuration for each of
the elements involved. The end result is that the compound formed has a net
electronic charge of zero as was discussed in the section onoxidation numbers.
Example: Let us write the formula for Potassium iodide.
Potassium has an oxidation state of +1. (K+1)
Iodine has an oxidation state of –1. (I-1)
The formula is KI. +1 + (-1) = 0
Formulas contain two types of position numbers, superscripts and subscripts.
Superscripts are written above and to the right of the symbol.
Subscripts are written below and to the right of the symbol.
Where no subscript number appears, it is inferred to be one,
because by definition a symbol represents one atom of an element.
In chemical formulas, superscripts represent the oxidation numbers,
whereas subscripts represent the definite proportion by weight in which
the elements combine in order to achieve the inert-gas configuration
(a net charge of zero).
Any time two elements with the same oxidation numbers of opposite
charges combine there is no need for subscripts.
Example: Ca+2 + 0-2
CaO
Problems arise when the oxidation numbers are different. Subscripts
are necessary in this case. For our purposes, we can simply write the
formula by crossing down the oxidation numbers.
Ca+2 + Cl-1
CaCl2
Remember we do not need to write the one, it is understood.
The sum of the oxidation numbers is still zero.
(+2) + 2(-1) = 0
Calcium is a metal so it is written first in the formula. Chlorine is the
Non-metal and is written last in the formula.
Sometimes a group of atoms behave as if they were a single atom. This
group has its own charge and is called a polyatomic ion. When writing
a formula containing a polyatomic ion, the rules are the same. The
positive part goes first, the negative part goes last, and the net charge
must equal zero.
Let us write a formula for magnesium hydroxide. Hydroxide is a
polyatomic ion.
Mg +2 + OH -1
Mg(OH)2
Notice that the entire polyatomic ion is contained within
parenthesis. The entire ion is multiplied by the two in order to
make the net charge equal to zero.
The charge on Mg is +2
O is 2(-2)
H is 2(+1)
Therefore, (+2) + 2(-2) + 2(+1) = 0
If we don’t place the parenthesis around the OH then we are
implying that only the H is multiplied by two and we have:
Mg is +2
O is –2
H is 2(+1)
(+2) + (-2) + 2(+1) = +2
Let us now write the formula for copper (II) oxide. The II
implies that the copper is in the +2 oxidation state.
Cu+2 + O-2
Cu2O2
CuO
Both copper and oxygen have a subscript of 2 in the first formula.
We can simplify by dividing both by 2 to get subscripts of 1.
The following is list of polyatomic ions, their charges and
formulas:
Name
Ammonium
Bicarbonate
Hypochlorite
Hydroxide
Nitrate
Nitrite
Carbonate
Sulfate
Sulfite
Phosphate
Cyanide
Formula/charge
NH4+1
HCO3-1
CLO-1
OH-1
NO3-1
NO2-1
CO3-2
SO4-2
SO3-2
PO4-3
CN-1
NAMING OF COMPOUNDS – There are four types of inorganic compounds: acids,
bases, salts and oxides. Although each one of these types has its own method of naming,
there is a more general way to name all compounds according to their formulas.
The simplest situation is one in which there is a compound containing a metal and
a polyatomic ion. The metal is named first, and the ion second.
If we have the compound KNO3, we name the metal first; potassium.
We name the polyatomic ion second; nitrate. The compound is called
Potassium nitrate.
Another situation involved in naming compounds occurs when a metal element
is combined with one other nonmetallic element. In these cases, the name of the
metallic element remains intact, but the nonmetallic element acquires an “-ide”
suffix.
Al2O3 is named aluminum oxide
Mg3N2 is named magnesium nitride
NaCl is name sodium chloride
KBr is named potassium bromide
H2O may be called hydrogen oxide
In all of the examples given, the names of the compounds did not reflect the
presence of subscript numbers. If however, there is more than one possible
combination of the constituents of a compound, then the subscript numbers do
influence the name.
CO is named carbon monoxide
CO2 is named carbon dioxide
SO2 is named sulfur dioxide
SO3 is named sulfur trioxide
Another influence on the naming of compounds is the oxidation state of certain
elements called “bivalent metals”. These metals have two possible oxidation
states. When naming compounds containing these metals, we must indicate
which oxidation state the metal is in.
In the older method of naming the suffix “-ous” is used to indicate the lower
oxidation state, and the suffix “-ic” is used to indicate the higher oxidation state.
For example:
Cu (+1) = cuprous
Cu (+2) = cupric
Hg (+1) = mercurous
Hg (+2) = mercuric
Fe (+2) = ferrous
Fe (+3) = ferric
So the compound CuO is called Cupric oxide because the copper is in the
higher oxidation state (+2). Remember we initially get Cu2O2 and then
divide both twos by two.
The newer method of naming is much simpler. The oxidation state is indicated by
Roman numerals in parenthesis.
Under the new method our compound CuO is called Copper (II) oxide.
EQUATIONS – Symbols are abbreviations for elements and formulas are abbreviations
for compounds. An EQUATION is an abbreviation for a chemical change. We will
discuss four types of these changes: synthesis, decomposition, double replacement
hydrolysis, and double-replacement neutralization.
Writing Equations – When we wrote the formulas for all of the previous
compounds, we expressed the end result of a chemical change called
SYNTHESIS. For example combine copper with oxygen to form copper (II)
oxide.
Cu0 + O20
Cu+2O-2
This is a synthesis reaction.
Notice that the net charge equals zero. The zeroes on the left hand side of the
equation indicate that neutral atoms do not express their oxidation numbers until
they are in a compound. We have written an equation. The arrow expresses a
principle called the “Law of Conservation of Mass”. This law may be stated as
follows: In a chemical change, matter is neither created nor destroyed, merely
changed from one form to another. In other words, the total amount of what is
produced is equal to the total amount of starting material.
Substances written to the left of the arrow are REACTANTS, and to the
right of the arrow, PRODUCTS. One way to identify synthesis reactions
is that there are two reactants, but only one product.
Notice that oxygen on the left hand side of the equation has a subscript of 2.
Because of their structures, certain atoms take the form of diatomic molecules.
Whenever they are written by themselves, they must contain a subscript of
two. Other elements that occur as diatomic molecules are: Hydrogen, oxygen,
nitrogen, fluorine, chlorine, bromine, and iodine. They may or may not have
a subscript of 2 when they are combined with another element.
DECOMPOSITION – The second type of chemical change is decomposition.
Decomposition is the opposite of synthesis and is defined as the breakdown of a
compound into its constituent parts. It is an extremely important reaction, since it
is the process which embalming attempts to retard. Just as a synthesis reaction
may be identified by the presence of two reactants and one product,
decomposition is identified by the presence of one reactant and two products.
A good example of a decomposition reaction is what happens when a
current of electricity is passed through water.
2H2O
2H2 + O2
Notice that hydrogen and oxygen have the subscript of 2 when they
are written by themselves.
Another example is the decomposition of mercuric(indicates higher
oxidation state) oxide by heat.
2HgO

2Hg + O2
The triangle is the Greek letter delta and is the symbol chemists use for
heat.
DOUBLE-REPLACEMENT (METATHESIS) REACTIONS – The third major
type of chemical reaction is double-replacement. Two significant examples are
neutralization and hydrolysis. Both of these are integral to the understanding of
what is to be accomplished during embalming. Double-replacement reactions are
identified by the presence of two reactants and two products. The Products are
obtained by changing partners of the plus and minus parts of the reactants.
Consider the reaction between NaOH (sodium hydroxide) and HCl
(hydrogen chloride). This is a NEUTRALIZATION reaction. The
definition of a neutralization is the reaction of an acid and a base to
produce salt and water.
Na+OH- + H+Cl-
or
HOH + NaCl
NaOH + HCl
Base
H+OH- + Na+Cl-
Acid
Water
Salt
The products are obtained by switching the Na+ for the H+. Thus both
parts are replaced (double replacement).
The same type of equation can be written for the reaction between
Aluminum hydroxide and hydrogen sulfate.
2Al+3(OH)3-1 + 3H2+1SO4-2
or
2Al(OH)3 + 3H2SO4
Base
Acid
6H+1OH-1 + Al2+3(SO4)3-2
6HOH + Al2(SO4)3
Water
Salt
There are a few things we should notice about these equations.
1. The compound HOH is simply water written a different way.
2. The polyatomic ions OH and SO4 are enclosed in parenthesis
when they are followed by a subscript other than the one that is
part of the polyatomic ion. Remember, this is so
that we multiply the entire ion by the subscript to obtain a
neutral molecule.
3. The numbers in front of the formulas are called
coefficients.
They are written to ensure that we are following the Law
of Conservation of Matter. We can not have one atom of
aluminum on the left and two on the right.
4. All we have done in the above equations is switch the positive
ions.
5. Equations are normally written without the presence of
oxidation numbers.
We can also write a double-replacement reaction called a HYDROLYSIS
reaction. The definition of hydrolysis is a chemical reaction in which a substance
is broken down or dissociated by water; a reaction between a salt and water to
yield an acid and a base of unequal strengths. An example is the reaction of
copper (II) sulfate with water.
CuSO4 + 2HOH
Salt
Water
Cu(OH)2 + H2SO4
Weak base
Strong acid
Notice that in the neutralization reaction water appears to the right of the arrow
(product), and in the hydrolysis reaction water appears to the left of the arrow
(reactant)
WEEK 3
RADIATION CHEMISTRY
Some forms of matter undergo a type of change that involves the nuclei of atoms. As a
result of some nuclear processes, a reactant atom is transformed into another type of atom
because of alterations in the composition of its nucleus.
RADIOACTIVITY – If the proton-proton repulsions are not minimized within a nucleus,
the nucleus decays to a more stable form. This spontaneous decay of nuclei is called
radioactivity. All elements with atomic numbers above 83 and some with lower atomic
numbers are naturally radioactive.
Types of Radioactivity:
ALPHA: This form of radiation consists of particles that each contain two
protons and two neutrons. Because their atomic number is 2, they are equivalent to
nuclei of helium. Each particle has double positive charge. The velocity of these
particles is approximately one-tenth the speed of light. Because of their mass and charge,
alpha particles travel only a few centimeters in air. It is possible to stop them by a piece
of paper. Since they can penetrate body tissue only about 0.05 millimeter, they cannot
reach internal organs from outside the body. If ingested or inhaled, alpha particles will
damage cells of internal organs. This damage is caused by the high ionizing power of
alpha particles. Their +2 charge causes them to remove electrons from the outer energy
levels of other atoms. They can be represented as follows:
4
2 He
BETA: Consists of very small particles that have a mass of 1/1837 that of a
proton. There are two types of Beta radiation. The more familiar type of beta particle
has a charge of –1 and is an electron. The less familiar particle is the positively charged
beta particle which is called a positron. Electrons are formed within a nucleus by the
breakdown of a neutron into a proton and an electron. The proton remains in the nucleus;
the electron is emitted. If, in contrast, a proton is broken down to a neutron within a
nucleus, a positive beta particle, the positron, is emitted from the nucleus.
The equation for the formation of the electron is as follows:
1
1
0
1
n
p + -10e
The equation for the formation of the positron is as follows:
1
p
1
1
0
n
+
+1e
0
In each equation the superscripts refer to mass numbers and the subscripts to charges.
Because beta particles are smaller in mass and in charge than alpha particles, they have
less ionizing power but can penetrate matter farther than alpha radiation. Their range in
air is several meters. They can be stopped by a thin piece of aluminum foil or plastic.
Their penetration of a few millimeters into living tissues causes damage both external and
internal. Prolonged external exposure to beta particles can burn the skin.
GAMMA RAYS: The most penetrating type of radiation from a radioactive atom
is gamma radiation. It is a type of electromagnetic radiation like visible light and x-rays.
Gamma rays travel as waves, but they are generally higher in energy. Frequently, gamma
rays are emitted from a nucleus during the process of either alpha or beta decay. In air,
gamma rays can travel many meters. Lead is necessary to stop them. Gamma rays
penetrate the human body and can damage both the cells and the tissues of internal
organs. The ionizing ability of this form of radiation is less than that of alpha or beta
particles.
Both alpha decay and beta decay lead to the conversion of an atom of one element
into an atom of another. This type of nuclear change is called TRANSMUTATION.
ALPHA DECAY: As the result of alpha decay, the mass number of the reactant
(decaying atom) is decreased by 4 and the atomic number is decreased by 2. The identity
of the product atom is determined by the new atomic number. For example:
238
234
4
92 U
90Th + 2 He
Uranium has gone through alpha decay to become thorium with a new atomic number of
90.
BETA DECAY: The thorium-234 produced by the alpha decay process
previously described is also radioactive. It decays by emission of a negative beta particle
and a gamma ray:
234
90 Th
234
0
91 Pa +-1e
+gamma rays
Because the mass of an electron is so much less than that of a proton, it is given a mass
number of zero. The atomic number of –1 is assigned to an electron. The alpha decay or
uranium-238 begins a series of decays called a radioactive disintegration series. The
series ends with the formation of lead-296, a stable atom. Each of the decaying atoms in
the series is referred to as a RADIONUCLIDE. This is a general term used to describe
any radioactive material.
HALF-LIFE: The stability of radionuclides is evaluated in terms of half-life,
symbolized by t1/2. The half-life of a particular radioactive atom is the amount of time
that it takes for half of the initial amount of radioactive material to decay.
Example: The half-life of radon-222 is 3.8 days. If initially 10,000 grams of this
radionuclide are present in a sample, there will be 5,000 grams left unchanged
after 3.8 days. The other 5,000 grams will have undergone the characteristic
decay pattern of this isotope or radon. After another 3.8 days, we will now
have 2,500 grams of the radon left.
The greatest amount of decay occurs in the first few half-lives. The longer the half-life,
the more stable the radioactive atom. Radionuclides used in medical procedures have
short half-lives. These materials, therefore, are not long-term radiological hazards.
ARTIFICIAL TRANSMUTATIONS: It is possible to cause a transmutation by
bombarding nuclei of one element with other particles. The first artificial nuclear
transformation was performed in 1919. By bombarding nitrogen gas with alpha particles
having a high velocity, an unstable isotope of fluorine was formed:
14
7
18
4
9F
N + 2 He
Decay of the fluorine atom produced a stable form of oxygen and a proton:
18
F
9
17
8O
+ 11H
The significance of this experiment was the first detection of protons. Neutrons were
discovered in 1932 by a bombardment reaction of beryllium with alpha particles:
9
4
Be
+
He
2
4
12
6
C + 01n
Bombardment reactions are the basis of the process of nuclear fission, splitting a nucleus
into smaller fragments. Nuclear reactors in Nuclear power plants operate under
conditions of controlled fission. Most of the energy released is in the form of heat.
Absorption of this heat by liquid coolants, such as water, generates steam. The steam can
then be used to drive a turbine to produce electricity. All the elements with atomic
numbers greater than uranium have been artificially produced in the laboratory by
bombardment reactions.
RADIATION TERMS: The following is a list of terms with which you should be
familiar.
1. EXPOSURE: evaluates the ability of gamma rays to produce ions in air. It is
defined as the amount of ionization or charge produced per unit mass of air by
gamma rays.
2. ABSORBED DOSE: The amount of energy absorbed by a unit mass of
matter.
3. DOSE EQUIVALENT: Used to compare the biological effects of the different
forms of radiation.
4. ACTIVITY: Gives the nuclear transformation rate of a decaying atom.
RADIATION DETECTORS:
Survey Meters:
1. Geiger-Mueller counter: Able to measure alpha, beta and gamma
radiation.
2. Scintillation counter: Also able to measure alpha, beta and gamma
radiation.
Dosimeters: measure individual exposures to radiation.
1. Film badges: Photographic film is darkened on exposure to radiation.
2. Pocket dosimeters: used for the detection of gamma rays.
3. TLDs: Chemical compounds release light proportional to the radiation
dose when processed
PROTECTION FROM RADIATION: Excessive radiation is harmful to humans. As radiation
travels through living tissue, the interaction may form highly reactive particles called free radicals.
A free radical has an unpaired electron that causes it to continue to react after its formation. If these
reactions occur in the nucleus of a cell, the molecules of the genes may be altered. Some of the
effects could be death of the cell, formation of a malignant carcinoma, or transmission of a genetic
mutation. We must consider three factors when protecting ourselves against radiation.
1. TIME: Minimizing the amount of time one is in contact with a radioactive material is a
protective measure against radiation.
2. DISTANCE: Measurement of the intensities of radiations at various distances from a
source shows that the intensity decreases with the square of the distance from the source.
We can express this mathematically as:
I  1/d2
This means that if we are at a distance of 2 meters from a source of radiation, the intensity is
one-fourth of what it is at the source itself.
3. SHIELDING: A very effective protection against radiation. Radionuclides are
usually stored in lead containers for this purpose.
SOURCES OF RADIATION ENCOUNTERED BY EMBALMERS
The two most common examples of radiation that are found in a human remains are due to:
1. Occupational exposure
2. Radionuclide Therapy
OCCUPATIONAL EXPOSURE: The first source is the less likely to pose a
problem to the embalmer for two reasons. First there have been only 112 fatal
radiation accidents in the world over a period of 53 years. Second, a body that has
been contaminated with dangerously high levels of radiation will not be released to the
embalmer until radiation levels have been reduced to an acceptable level by standard
decontamination procedures. By the time the embalmer receives one of theses remains,
the only problems that should be encountered will be those associated with delayed
embalming and refrigerated or frozen bodies.
RADIONUCLIDE THERAPY: High levels of radiation can occur during
treatment of malignant diseases. Patients receiving large doses of radionuclides are
usually required to remain hospitalized until their content of radioactivity is less than
30 mCi. This requirement, which is called the 30 mCi rule, may not be the best
criterion for release of a patient. A better criterion is that patients remain hospitalized
until their content of radiation is low enough to cause a dose no greater than 0.1 rem to
individuals with which they make contact
Radionuclides are not given to moribund patients. Consequently, deceased
patients with large amounts of radionuclides will be encountered only rarely. Hospital
personnel are required by the conditions of a license for the use of these substances to
monitor and certify to the embalmer the radioactive condition of the patient.
VEHICLES OF RADIONUCLIDE THERAPY: Common methods by
which radionuclides are introduced into a body are by ingestion, injection, and
implantation. Radioactive colloids may be injected directly into localized malignant
growths. Implants are usually in the form of radioactive needles, seeds, wires, and
pellets. Ingested and injected radionuclides are generally disseminated throughout
body fluids, organs, and their protective serous membranes. Implanted materials
usually remain in one place, unless the accidental rupture of seeds, pellets, or needles
causes generalized dissemination. The danger to the embalmer from any of the ante
mortem treatments is influenced by whether or not an autopsy has been performed.
PREPARATION OF THE BODY WITHOUT AUTOPSY: Embalmers
rarely will be exposed to high levels of radiation from patients treated with
radionuclides who die outside the hospital. Provided these bodies are embalmed
without opening the cavities, the exposure to the embalmer will most likely be
minimal. The major protective measure that should be taken during such an
embalming is wearing rubber gloves. They prevent possible contamination by
radioactive body fluids. In addition, a waterproof apron should be worn over the
standard protective clothing. Lead aprons serve no useful purpose. Effective
protection against gamma radiation requires an apron with several inches of solid lead.
Time, distance, and shielding are the keys to the control of exposure to radiation. Of
the three, shielding has the least significance to the embalmer.
More elaborate procedures may need to be taken in an unautopsied case if a patient
dies within a few hours of being treated internally with phosphorus-32. This
radionuclide is injected as a colloidal suspension. When introduced into the abdomen,
it contaminates serous fluids by settling out on the surface of serous membranes.
Embalmings of theses cases should be performed in the hospital autopsy room under
the direction of a radiation protections supervisor. Special precautions include removal
of the serous fluid from the body by a trocar that is fixed so that no person must hold it
or the tubing while the fluid is being withdrawn. Such fluid should be aspirated into a
closed system followed by flushing into the sewer system with LARGE amounts of
water. The blood and urine may be disposed of normally, because they contain no
appreciable radioactive material.
In contrast, the blood and urine of a patient who dies during the first 24 hours after
administration (orally or intravenously) of iodine-131 may contain considerable
amounts of radioactivity. These fluids should be aspirated and disposed of like the
serous fluid contaminated with the colloidal suspension.
PREPARATION OF THE AUTPOSIED BODY: Radiation encountered
from nonautopsied bodies is in the form of gamma rays, which have the highest
penetrating power of the three types previously described. Radiation exposure from
autopsied remains involves beta particles in addition to gamma rays. Once any
implants placed in the body have been removed, the body no longer contains
radioactivity. Implants should never be touched directly with the hands.
CREMATION: If a body is to be cremated without embalming, there will
be no radiation hazard from external handling. People living in the area of the
crematory may be exposed to radioactive material emitted with the stack gases.
Employees of the crematory may also be exposed to radioactivity by inhaling the dust
of the remains. It is required that all implants be removed prior to cremation under the
direction of a radiation protection representative.