CHEM 120 Module 1: The Periodic Table
Recent Developments & New Directions
page 1 of 12

1.1 Elements: The “building blocks” of all materials
At the present time, there are 118 known elements. Over time,
and with contributions from many scientists, these elements
have been arranged into a single document (the periodic table),
one of the most recognizable icons in science.
For chemists, the periodic table is a tool that serves to organize
their discipline. It helps them rationalize and unify what has
already been discovered about the known substances and their
reactions. It also guides their thinking about substances and
reactions that are still to be discovered.
Did you know? Elements 1 through 92, with the exception of elements 43 (Tc) and 61 (Pm), occur naturally
on Earth. On the other hand, elements 93 through 118 must be synthesized in particle accelerators. Elements
with the highest atomic numbers are typically produced in very small quantities, only a few atoms at a time.




















Did you know? To incorporate the lanthanoids and actinoids into their proper spots in the 6th and 7th
periods, we would have to expand the periodic table to 32 columns. A periodic table with 32 columns is
inconveniently wide, so the lanthanoids and actinoids are usually listed at the bottom of the table.


1


18
1
H
1.008


2


13


14


15


16


17
2
He
4.0026
3
Li
6.94
4
Be
9.0122
5
B
10.81
6
C
12.011
7
N
14.007
8
O
15.999
9
F
18.998
10
Ne
20.180
11
Na
22.990
12
Mg
24.305


3



4


5


6



7


8



9


10



11


12
13
Al
26.982

14
Si
28.085
15
P
30.974

16
S
32.06
17
Cl
35.45
18
Ar
39.948
19
K
39.098
20
Ca
40.078
21
Sc
44.956
22
Ti
47.867
23
V
50.942
24
Cr
51.996
25
Mn
54.938
26
Fe
55.845
27
Co
58.933
28
Ni
58.693
29
Cu
63.546
30
Zn
65.38
31
Ga
69.723
32
Ge
72.630
33
As
74.922
34
Se
78.96
35
Br
79.904
36
Kr
83.798
37
Rb
85.468
38
Sr
87.62
39
Y
88.906
40
Zr
91.224
41
Nb
92.906
42
Mo
95.96
43
Tc
(98)
44
Ru
101.07
45
Rh
102.91
46
Pd
106.42
47
Ag
107.87
48
Cd
112.41
49
In
114.82
50
Sn
118.71
51
Sb
121.76
52
Te
127.60
53
I
126.90
54
Xe
131.29
55
Cs
132.91
56
Ba
137.33
57-71
La-Lu
72
Hf
178.49
73
Ta
180.95
74
W
183.84
75
Re
186.21
76
Os
190.23
77
Ir
192.22
78
Pt
195.08
79
Au
196.97
80
Hg
200.59
81
Tl
204.38
82
Pb
207.2
83
Bi
208.98
84
Po
(209)
85
At
(210)
86
Rn
(222)
87
Fr
(223)
88
Ra
(226)
89-103
Ac-Lr
104
Rf
(261)
105
Db
(262)
106
Sg
(266)
107
Bh
(264)
108
Hs
(277)
109
Mt
(268)
110
Ds
(271)
111
Rg
(272)
112
Cn
113
Nh
114
Fl
115
Mc
116
Lv
117
Ts
118
Og


Lanthanoids
57
La
138.91
58
Ce
140.12
59
Pr
140.91
60
Nd
144.24
61
Pm
(145)
62
Sm
150.36
63
Eu
151.96
64
Gd
157.25
65
Tb
158.93
66
Dy
162.50
67
Ho
164.93
68
Er
173.05
69
Tm
168.93
70
Yb
173.05
71
Lu
174.97

Actinoids
89
Ac
(227)
90
Th
232.04
91
Pa
231.04
92
U
238.03
93
Np
(237)
94
Pu
(244)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
99
Es
(252)
100
Fm
(257)
101
Md
(258)
102
No
(259)
103
Lr
(262)


Notes:
1. The periodic table shown below is based on the latest release (December 1st, 2018) from the International
Union of Pure and Applied Chemistry (IUPAC). The highlighted elements are associated with very recent
changes to the periodic table, which are discussed in the following sections.
2. For H, Li, B, C, N, O, Mg, Si, S, Cl, Br, and Tl, the conventional atomic mass, a representative value from the
atomic mass interval, is provided.
3. For certain radioactive elements, the mass number of the most stable isotope is provided in (parentheses).
Astonishingly, these substances are
made up of only 90 naturally-occurring
elements.
FYI: Chemical Abstract Services (CAS) is a division
of the American Chemical Society (ACS). CAS
provides databases (for example, the CAS Registry)
and search tools (for example, SciFinder) for finding
chemical information.
The Chemical Abstract Services (CAS)
registry is arguably the best database for all
known compounds. Currently, it contains
information on over 143 million unique
chemical substances.
CHEM 120 Module 1: The Periodic Table
Recent Developments & New Directions
page 2 of 12

The Newest Elements
Elements 112 through 118 were recently added to the periodic table to complete the 7th period.








Did you know? When claims are made that a new element has been discovered, IUPAC reviews the
evidence, sorts out who gets credit for the discovery (when competing claims are made) and ultimately,
decides who gets to name the new element. According to IUPAC rules, an element can be named after a
mythological concept, a mineral, a place or country, a property, or a scientist.
The table below highlights some (hopefully, interesting) facts about a few other elements.


















Isotopes refer to atoms that have the same number of protons but a different number of neutrons in their
nuclei. Allotropes refer to different molecular forms of the same element. For example, graphite, diamond,
and buckminsterfullerene (C60) are allotropes of carbon. S2, S8, and S20 are allotropes of sulfur.
Element Symbol Name Added
112 Cn copernicium 2010
113 Nh nihonium 2016
114 Fl flerovium 2012
115 Mc moscovium 2016
116 Lv livermorium 2012
117 Ts tennessine 2016
118 Og oganesson 2016


The first element to be
discovered?
Although metallic elements such as gold, silver, tin, copper, lead and
mercury were known and used for many centuries, phosphorus (P) is
considered the first element to be discovered scientifically. It was
isolated in 1669 by Hennig Brandt, a German chemist, from samples
of his own urine.
Most abundant elements, by
mass, in the Earth’s crust?
oxygen (O) > silicon (Si) > aluminum (Al) > iron (Fe)
Most abundant elements, by
mass, in the human body?
oxygen (O) > carbon (C) > hydrogen (H) > nitrogen (N)
Most abundant elements, by
mass, in the universe?
hydrogen (H) > helium (He) > oxygen (O) > carbon (C)
Densest elements? osmium (Os) > iridium (Ir) > platinum (Pt)
22.6 g cm−3 22.5 g cm−3 21.5 g cm−3
Which elements have the
most isotopes?
Cesium (Cs) and xenon (Xe) each have 36 known isotopes.
Which elements have the
most allotropes?
According to the Samara Carbon Allotrope Database (SACADA),
http://sacada.sctms.ru/), carbon (C) has more than 500 different
allotropic forms. Sulfur (S) has a few dozen allotropic forms.
The only elements to be
named after a living person
at the time of naming?
Seaborgium (Sg) and Oganesson (Og) were named after Glenn T.
Seaborg (b. 1912, d. 1999) and Yuri Oganessian (b.1933) to honour
their contributions to the discovery of many heavy elements.

Did you know? These elements have been made only
a few atoms at a time, but that does not stop scientists
from speculating on their properties.
For example, some scientists have predicted that Cn
will be a liquid metal like mercury but more volatile.
Others have suggested it will be very unreactive and
more like a noble gas than a metal.
There is also an interesting debate about the properties
of Og. Some scientists have predicted that, unlike the
noble gases above it, Og will be a liquid or solid at room
temperature and possibly quite reactive.
CHEM 120 Module 1: The Periodic Table
Recent Developments & New Directions
page 3 of 12

1.2 The Measurement and Evolution of Atomic Masses
The measurement of atomic mass was central to the emergence of chemistry as a
scientific discipline, and the development of the periodic table. Prior to 1858, several
sets of atomic weights were in use, each assigning different relative masses to the
known elements. The uncertainty over atomic masses persisted until scientists
recognized that some elements consisted of molecules, not individual atoms.
The first set of reliable atomic masses, reported in 1858 by the Italian chemist
Stanislao Cannizzaro, were obtained from measurements of gas volumes and
application of Avogadro’s law: Equal volumes of different gases, compared at the
same temperature and pressure, contain equal numbers of molecules.
With estimates of atomic masses in hand, Dmitri Mendeleev, a Russian chemist,
showed that when the elements that were known at the time were arranged in order
of increasing atomic mass, their properties seemed to repeat in a regular way. In
1869, he presented a tabular arrangement of elements that placed elements with
similar properties in the same vertical column (group), leaving gaps in certain places
for elements he believed had not yet been discovered. The validity of Mendeleev’s
arrangement was reinforced by the fact that seven of the 10 elements he predicted
were eventually discovered. (See page 378 in Petrucci, 11th edition, for a
reproduction of Mendeleev’s periodic table.)
In Mendeleev’s table, the elements were arranged essentially in order of increasing
atomic mass. However, to place elements with similar properties in the same group,
Mendeleev had to place some elements “out of order” with respect to their atomic
masses. We now know that the correct ordering principle is atomic number, not
atomic mass. In the modern version of the periodic table, the elements are in order
of increasing atomic number. (The atomic number of an element is equal to the
number of protons in the nucleus of any of its atoms.)
Did you know? Although Mendeleev is widely considered the “father” of the periodic
table, that honour should be shared with Lothar Meyer, a German chemist. Meyer
developed a similar but abbreviated version of the periodic table several years before
Mendeleev. However, Mendeleev’s version was the first to be published and
therefore, the first to be widely disseminated to the scientific community.

CHEM 120 Module 1: The Periodic Table
Recent Developments & New Directions
page 4 of 12

Mass Spectrometry
(If you’re interested, see http://www.chemguide.co.uk/analysis/masspec/howitworks.html for additional information.)
These days, atomic masses can be measured with a very high degree of accuracy using a mass
spectrometer. A mass spectrometer operates on the principle that an atom or molecule, once ionized,
can be deflected by a magnetic field. The extent to which the particle is deflected from its original path
depends on the speed of the particle, the strength of the magnetic field, and the mass-to-charge ratio,
m z , of the ionized atom or molecule.
A particle goes through the following stages as it passes through a mass spectrometer.
1. Ionization: A gas sample is ionized, with formation of +1 ions being highly favoured. The first
mass spectrometers used bombardment with high energy electrons to knock off one or more
electrons from each atom or molecule. Modern instruments use other methods of ionization.
2. Acceleration: The positive ions are accelerated into a finely focused beam by electrically charged
velocity selector plates. Only ions with a specific velocity make it through to the magnetic field.
3. Deflection: The positive ions that reach the magnetic field all have the same velocity. However,
their paths will be deflected to varying extents depending on the mass and charge of the ion. Lighter
(less massive) ions are deflected to a greater extent than heavier ions. Ions with higher charges are
deflected to a greater extent than ions with smaller charges. Consequently, the finely focused beam
that entered the magnetic field is split into components of different mass-to-charge ratios. Since the
conditions typically favour the formation of +1 ions, the incoming beam is split essentially into beams
of ions with different masses.
4. Detection: The different beams of ions strike different regions of the detector. The greater the
number of ions of a given type, the greater the intensity of the response from the detector. Thus, the
detector provides a measure of the number of ions of each type, which is represented graphically as
a mass spectrum. A mass spectrum is a graph of intensity versus the mass-to-charge ratio.







▲ The image on the left is a schematic diagram of a mass spectrometer. A finely focused beam of Ge ions is
split into different components by a magnetic field that is perpendicular to the plane of the page. The image on
the right is a mass spectrum. It provides information about the relative amounts and masses of the ions.
CHEM 120 Module 1: The Periodic Table
Recent Developments & New Directions
page 5 of 12

Atomic Mass Intervals and Conventional Atomic Masses
Technological improvements in mass spectrometry have provided highly accurate measurements of
atomic masses. For example, the mass of 13C has been measured accurate to 12 figures. (See the table
below.) These highly accurate measurements have led to the discovery that, for certain elements, the
isotopic abundances vary from one sample to another. For example, the isotopic abundance of 13C
ranges from 0.9629% (in samples obtained from the ocean bottom in the Northern Pacific) to 1.1466%
(in samples of deep sea pore water). This discovery contrasts the previously held view that the isotopic
abundances (and therefore, the average atomic mass) of an element were constants of nature.
To understand the implications of this discovery, we must first discuss the concept of average atomic
mass. For elements that have two or more isotopes, the (average) atomic mass, mav, is the weighted
average of the masses, mi, of its isotopes. The weights, wi, are the fractional isotopic abundances (i.e.,
the isotopic abundances expressed as decimal numbers with values between 0 and 1).
=
=  i i
i
m w m
# of
isotopes
av
1

Using this formula, and the data below for carbon, we find that the average atomic mass of carbon has
values between 12.0096 u and 12.0116 u.





For this reason, IUPAC recommends that the average atomic mass of carbon, and that of several other
elements, be reported as an atomic mass interval, not as a single specific value. (See the table on the
next page.) For carbon, the atomic mass interval is given as [12.0096, 12.0116] to indicate that the
average atomic mass of carbon, in any material normally encountered, is greater than or equal to
12.0096 u and less than or equal to 12.0116 u.
For elements with atomic masses given as intervals, IUPAC also provides conventional atomic mass
values. These values can be used when a specific, representative value of the atomic mass is required.
These conventional values have been selected so that, for materials normally encountered, the atomic
mass should be within in an interval of plus or minus one in the last digit.
12C 13C
Isotopic masses
12 u
(defined)
13.0033548378 u
(from mass spectrometry)
Fractional abundances for samples from
the ocean bottom in the Northern Pacific
0.988534 0.011466
Fractional abundances for samples from
deep sea pore water
0.990371 0.009629

CHEM 120 Module 1: The Periodic Table
Recent Developments & New Directions
page 6 of 12

Atomic Mass Intervals and Conventional Atomic Masses for Selected Elements





















Summary of key ideas

The atomic mass interval is used for certain elements to indicate the range of values expected for
the atomic mass because of observed variations in the isotopic abundances of these elements. The
interval is expressed in the form [a,b], which indicates that the atomic mass will be greater than or
equal to a atomic mass units and less than or equal to b atomic mass units.

The conventional atomic mass is provided for elements having their atomic masses defined in
terms of an atomic mass interval and may be used in situations when a representative value of the
atomic mass is required.
Atomic
Number
Atomic
Symbol
Atomic Mass, u
Interval Conventional
1 H [1.00784, 1.00811] 1.008
3 Li [6.938, 6.997] 6.94
5 B [10.806, 10.821] 10.81
6 C [12.0096, 12.0116] 12.011
7 N [14.00643, 14.00728] 14.007
8 O [15.99903, 15.99977] 15.999
12 Mg [24.304, 24.307] 24.305
14 Si [28.084, 28.086] 28.085
16 S [32.059, 32.076] 32.06
17 Cl [35.446, 35.457] 35.45
35 Br [79.901, 79.907] 79.904
81 Tl [204.382, 204.385] 204.38

Note carefully: The interval
designation [a, b] does not imply
any statistical distribution of values
between the lower and upper
bounds nor does it represent a
measure of the statistical
uncertainty. For example, the
average of a and b is neither the
most likely value nor the most
representative value. The difference
b – a does not represent the
uncertainty.
CHEM 120 Module 1: The Periodic Table
Recent Developments & New Directions
page 7 of 12

Example 1-1: Bromine has two naturally occurring isotopes, bromine-79 and bromine-81, with masses of
78.918338 u and 80.916291 u, respectively, and an atomic mass interval of [79.901, 79.907]. Estimate
the variation in the percent isotopic abundance of 79Br using (a) the lower bound; and (b) the upper bound
of the atomic mass interval.



CHEM 120 Module 1: The Periodic Table
Recent Developments & New Directions
page 8 of 12

Example 1-2: A 0.2522 g sample of a mixture of LiCl and NaCl was treated with excess of AgNO3 solution,
yielding a precipitate of AgCl. The precipitate was filtered, dried, and weighed. The mass of the precipitate
was 0.7068 g. Calculate the lower and upper bounds for the percentage by mass of LiCl in the sample.
Hint: Perform two calculations. In the first calculation, use the lower bound of the atomic mass intervals
for Li and Cl. In the second calculation, use the upper bounds. Use the atomic masses provided in this
module and retain all digits in intermediate calculations and round off at the end.
Solution:
There are two reactions contributing to the formation of AgCl.
LiCl(aq) + AgNO3(aq) ⎯⎯→ AgCl(s) + LiNO3(aq) reaction 1
NaCl(aq) + AgNO3(aq) ⎯⎯→ AgCl(s) + NaNO3(aq) reaction 2
Therefore:: total moles of AgCl = moles of AgCl from reaction 1 + moles of AgCl from reaction 2
n n nAgCl LiCl NaCl
1 1
= × + ×
1 1

Let the mass of LiCl be m grams. Therefore, the mass of NaCl is (0.2522 – m) grams.
The expression above for nAgCl can be re-written in the following form.

−m m
M M MAgCl LiCl NaCl
0.7068 g 1 (0.2522 ) g 1
= × + ×
1 1

This is one equation in one unknown. We can re-arrange it to obtain the following expression for m.

 
− + 
  
= m
M M M MAgCl LiCl NaCl NaCl
0.7068 g 1 1 0.2522 g
−

−
M M
m =
M M
AgCl NaCl
LiCl NaCl
0.7068 g 0.2522 g
1 1

The results below indicate that the mixture is between 37.68% and 37.92% LiCl by mass.









. Molar Masses Results
Using the lower bounds
of the atomic mass
intervals for Li and Cl
MAgCl = 143.316 g mol
−1
MLiCl = 42.384 g mol
−1
MNaCl = 58.436 g mol
−1
m = 0.09503
 % LiCl = 
0.09503 g
100 = 37.68
0.2522 g

Using the upper bounds
of the atomic mass
intervals for Li and Cl
MAgCl = 143.327 g mol
−1
MLiCl = 42.454 g mol
−1
MNaCl = 58.447 g mol
−1
m = 0.09563
 % LiCl = 
0.09563 g
100 = 37.92
0.2522 g



CHEM 120 Module 1: The Periodic Table
Recent Developments & New Directions
page 9 of 12

1.3 Using Atoms Wisely: Atom Economy and the E-factor
Ultimately, chemistry is about transformation: re-arranging the atoms in a given set of substances to form
another set of substances. The reasons for doing so are uncountable, but in part, to address the many
challenges society faces today.










Everything we have now, and for the foreseeable future, comes from the atoms that exist in limited
quantities here on Earth. Atoms are the “currency” of chemistry and, to a chemist, a valuable commodity.
Chemists have always been concerned with keeping track of the atoms they use. They strive to
maximize the yield of their reactions, by designing synthetic methods and processes that are efficient in
their use of atoms and which minimize waste.
The efficient use of atoms and the minimization of waste are central principles in green chemistry, a term
coined in the 1990s by the United States Environmental Protection Agency. Green chemistry is an
approach to chemistry that is intentionally focused on not only the efficient use of atoms (and energy) but
also chemical methods that reduce or eliminate reagents, products, solvents, by-products, wastes, etc. that
are hazardous to human health or the environment. Two of the principles of green chemistry are as follows.
(The Digging Deeper section on page 12 provides a full listing.)
(1) It is better to prevent waste than to treat or clean it up afterwards.
(2) Methods should be designed to maximize the incorporation of all materials used in the process into
the final product.
Atom economy and the E-factor are quantities that can be calculated by a chemist to help assess the
“green-ness” of a chemical reaction or process. Atom economy (expressed as a percentage) is defined in
terms of the theoretical amounts of reactants and products involved in a reaction or process.
= 100%
stoichiometric mass of the desiredproduct
% atom economy
mass of a stoichiometric mixture of reactants

The stoichiometric mass of the desired product is the maximum mass that can be expected from a
stoichiometric mixture of reactants. (In a stoichiometric mixture of reactants, the mole ratio of reactants is
CHEMISTRY
Providing new and
safer materials
Providing renewable
substitutes for dwindling
or scarce materials
Improving health and
conquering disease
Finding new sources
of energy
Monitoring and
protecting the
environment
CHEM 120 Module 1: The Periodic Table
Recent Developments & New Directions
page 10 of 12

equal to the ratio of the stoichiometric coefficients. None of the reactants is present in excess.) By
comparing atom economy values for different synthetic routes, a chemist can determine which provides the
“best” use of atoms in the reactants. Therefore, the concept of atom economy is helpful for choosing the
least wasteful synthetic route.
The E-factor is defined in terms of quantities that are easily measured and therefore, the E-factor is easily
calculated, no matter how many substances, reactions, or processes are involved.
=
mass of waste produced *
E - factor
mass of product obtained


A large value for the E-factor indicates that many kilograms of
waste are generated for every kilogram of product obtained. A small value for the E-factor is desirable.

The E-factor is particularly useful for real-time monitoring of the impact of making many changes in a
synthesis, process, or company. A company could easily calculate its E-factor, before and after making
changes, using “kilograms of raw materials purchased” and “kilograms of product sold”.
Example 1-3: Consider the following reactions. Which, if any, have 100% atom economy? Which, if any,
have an E-factor of zero?
















fyi: “E-factor” is an abbreviation for
“environmental factor”.
* If the reaction or process produces waste water,
the mass of the water is not included. However,
the masses of substances dissolved in the water
are included.
CHEM 120 Module 1: The Periodic Table
Recent Developments & New Directions
page 11 of 12

Example 1-4: Calculate the % atom economy for each of the following synthetic routes for converting
benzene, C6H6, to aniline, C6H5NH2.
Method 1: C6H6 + (CH3)3SiN3 + 2 F3CSO3H + NaOH
⎯⎯⎯→ C6H5NH2 + N2 + (CH3)3SiOSO2CF3 + NaF3CSO3 + H2O
Method 2: C6H6 + HNO3 ⎯⎯⎯→2 4
H SO
C6H5NO2 + H2O
C6H5NO2 + 3 H2 ⎯⎯⎯→

C6H5NH2 + 2 H2O


Solution:
The molar masses, in g/mol, are as follows.
C6H5NH2, 93.126
C6H6, 78.108 (CH3)3SiN3, 115.222 F3CSO3H, 150.088 NaOH, 39.998
HNO3, 63.018, H2, 2.016
For Method 1:
Focus on making 1 mole of C6H5NH2 (or 93.126 g C6H5NH2). We need 1 mole (or 78.108 g) of C6H6,
1 mole (or 115.222 g) of (CH3)3SiN3, 2 moles (or 2×150.088 g) of F3CSO3H, and 1 mole (or 39.998 g) of
NaOH. Thus:
×100% = 17%
93.126g
%atom economy =
78.108g + 115.222 g + 2×150.088 g + 39.998 g

For Method 2:
The overall process is obtained by adding the two consecutive reactions.
C6H6 + HNO3 + 3 H2 → C6H5NH2 + 3 H2O
Focus on making 1 mole of C6H5NH2 (or 93.126 g C6H5NH2). You need 1 mole (or 78.108 g) of C6H6,
1 mole (or 63.108 g) of HNO3, and 3 moles (or 3×2.016 g) of H2. Thus:
×100% = 63%
93.126g
% atom economy =
78.108g + 63.108 g + 3×2.016 g





Keep in mind: When comparing different
synthetic routes, a chemist must also consider
other practical matters including the ease of
isolation or purification of the desired product,
the potential for side reactions, and the toxicity
or hazards of the substances used.
CHEM 120 Module 1: The Periodic Table
Recent Developments & New Directions
page 12 of 12

⌈ Digging Deeper … Green Chemistry






















Evaluating the “true” green-ness of a reaction or process? Atom economy and the E-factor are useful for
evaluating how wasteful a reaction or process is, but they ignore the environmental impacts of the substances
involved. A complete assessment of the “green-ness” of a reaction or process also requires consideration of the
substances’ human toxicity, aquatic ecotoxicity, persistence in the environment, acidification potential, ozone
depletion potential, smog formation potential, and global warming potential.
Has green chemistry made a difference? Figures published by the U.S. Environmental Protection Agency
indicate that, every year in the U.S., green chemistry eliminates more than 6 million kilograms (60,000 metric
tonnes) of hazardous substances, saves more than 200 million litres of water, and prevents 25 million kilograms
(26,000 metric tonnes) of CO2 emissions.
A specific example? The industrial synthesis of ibuprofen (a medication for treating pain, fever, and inflammation)
was originally a 6-step process with an atom economy of about 40%. It is now made using a 3-step process that
has an atom economy of 77%. The new process eliminates millions of kilograms of waste each year. ⌋
The Twelve Principles of Green Chemistry
(Ref: P. T. Anastas and J. C. Warner, Green Chemistry: Theory and Practice, Oxford University Press: New York, 1998.)
1. Prevent waste: It is better to prevent waste than to treat or clean up waste after it has been created.
2. Atom economy: Synthetic methods should be designed to maximize the incorporation of all materials
used in the process into the final product.
3. Design less hazardous chemical syntheses: Synthetic methods should be designed to use and generate
substances that possess little or no toxicity to human health and the environment.
4. Design benign chemicals: Chemical products should be designed to provide their desired function while
minimizing their toxicity.
5. Use benign solvents and auxiliaries: The use of auxiliary substances (e.g., solvents, separation agents,
etc.) should be made unnecessary wherever possible and innocuous when used.
6. Design for energy efficiency: Energy requirements of chemical processes should be evaluated for their
environmental and economic impacts and should be minimized. If possible, synthetic methods should be
conducted at ambient temperature and pressure.
7. Use renewable feedstocks: A raw material or feedstock should be renewable rather than non-renewable
whenever technically and economically feasible.
8. Reduce derivatives: Unnecessary derivatization (e.g., the use of blocking or protecting groups) should be
minimized or avoided, because such steps require additional reagents and can generate waste.
9. Catalysis: Catalytic reagents are superior to consumable reagents. A catalyst is not consumed and can be
re-used to carry out additional transformations.
10. Design for degradation: Chemical products should be designed so that at the end of their function they
break down into innocuous degradation products and do not persist in the environment.
11. Real-time analysis for pollution prevention: Analytical methodologies need to be further developed to
allow for real-time, in-process monitoring and control prior to the formation of hazardous substances.
12. Inherently benign chemistry for accident prevention: Substances and the forms in which they are used
should be chosen to minimize the potential for chemical accidents, including releases, explosions, and fires.
Before you ask: You are not responsible for knowing these principles. They are included to provide context for the use of atom economy or
the E-factor as a measure of the “green-ness” of a reaction or process. Want a “pocket guide” from the American Chemical Society? Go to
https://www.acs.org/content/acs/en/greenchemistry/what-is-green-chemistry/principles/12-principles-of-green-chemistry.html
































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































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