History of the Periodic Table
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C HAPTER
Chapter 1. History of the Periodic Table
1 History of the Periodic Table
Lesson Objectives
• Describe the history of the periodic table and the contributions of Luther Meyer, John Newlands, Dmitri
Mendeleev, Ernest Rutherford, and Henry Moseley.
• Explain how the periodic table was originally organized and the inconsistencies in this first periodic table.
• Describe the relationship between atomic number and atomic mass.
• Describe our modern periodic table and how the elements are arranged.
Lesson Vocabulary
• periodic law: States that when elements are arranged in order of increasing atomic number, there is a periodic
repetition of their chemical and physical properties.
Check Your Understanding
1. What is the atomic weight and atomic number of the following element?
2.
3. What do atomic number and atomic mass tell us?
Introduction
The earliest versions of the periodic table of elements emerged in the mid-1800s. At that time, there were approximately 60 known elements. This table has evolved over time as additional elements have been discovered and the
known elements were arranged and categorized in slightly different ways. Today, there are 118 known elements,
which are generally arranged in the familiar form of a modern periodic table.
Atomic Mass and Periodic Properties
One of the major developments that allowed for what became known as the periodic table was the discovery and
measurements of atomic masses. With this discovery, some characteristic properties of the elements could be related
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to their relative atomic mass. This method for arranging the elements began in the early 1800s when John Dalton
(1766–1844) described elements and compounds in terms of relative weights. Using the knowledge available at the
time, Dalton prepared an early version of what later became the periodic table ( Figure 1.1).
FIGURE 1.1
Dalton’s Table of the Elements
Following Dalton’s work, scientists began relating chemical properties to atomic weight. This resulted in several
major discoveries, which led to the development of what we now know as the modern periodic table.
Other Early Attempts at a Periodic Table
Following the work of Dalton, a German scientist by the name of Julius Lothar Meyer (1830–1895) created a table
of elements that was organized based on the concept of valency, which has to do with the ratios in which one element
combines with another to make a compound.
Meyer published a textbook in 1864 where he presented his table of elements. Meyer’s table showed 28 elements
systematically arranged by valence into vertical columns. The atomic weights of these elements increase by similar
amounts when going stepwise from left to right across the table. There were, however, some major shortcomings of
Meyer’s table. Only a fraction of the known elements could be easily categorized by valence, due to the fact that
many elements can combine with one another in multiple different ratios (thus creating multiple different chemical
compounds).
Shortly after this, in 1865, a similar periodic table was published by English chemist William Odling (1829–1921).
Odling’s table described a systematic arrangement of 45 elements. However, some elements were omitted without
any reasonable explanation, and this version of the periodic table was quickly replaced by subsequent versions.
The Law of Octaves
Also in 1865, an English chemist by the name of John Newlands (1837–1898) published another version of the
periodic table ( Table 1.1). The arrangement was based on his proposed Law of Octaves, which stated that “if the
chemical elements are arranged according to increasing atomic weight, those with similar physical and chemical
properties occur after each interval of seven elements.”
TABLE 1.1: Newlands’ Law of Octaves Octaves
H
2
Li
Ga
B
C
N
O
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Chapter 1. History of the Periodic Table
TABLE 1.1: (continued)
H
F
Cl
Co, Ni
Br
Pd
I
Pt, Ir
Li
Na
K
Cu
Rb
Ag
Cs
Tl
Ga
Mg
Ca
Zn
Sr
Cd
Ba, V
Pb
B
Al
Cr
Y
Ce, La
U
Ta
Th
C
Si
Ti
In
Zr
Sn
W
Hg
N
P
Mn
As
Di, Mo
Sb
Nb
Bi
O
S
Fe
Se
Ro, Ru
Te
Au
Th
Newlands was one of the first to detect a periodic pattern in the properties of the elements and anticipated later
developments of this periodic law. However, Newlands’ table, like Meyer’s, did not gain widespread acceptance and
use, primarily because it required the omission of several known elements without any real explanation, and few
testable predictions could be made from his proposals.
Dmitri Mendeleev’s Periodic Table
At this point in history, the sharing of scientific information was not as systematic as it is today, so multiple scientists
could be working on the same ideas in different parts of the world without even realizing it. In 1869, Russian chemist
Dmitri Mendeleev (1834–1907) independently described an arrangement of about 60 elements based on increasing
atomic weight ( Figure 1.2).
FIGURE 1.2
Mendeleev’s Periodic Table
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Mendeleev’s table was similar to some of the other ones mentioned above, but it gained more widespread acceptance,
due in part to its predictions of properties for elements that were not yet known. Rather than omitting elements
where the periodic trends did not seem to fit, he left placeholders for elements that he predicted would eventually
be discovered. The predicted properties (including atomic mass, valence, and melting points) of "eka-boron", "ekaaluminum", and "eka-silicon" were found to be very close to those of the subsequently discovered elements scandium
(1879), gallium (1875), and germanium (1886). The discoveries of these elements provided very strong evidence in
support of Mendeleev’s table, and it provided the basis for our modern periodic table of the elements.
Here is a short video describing Mendeleev’s discovery: http://www.youtube.com/watch?v=rBroXfaavw0 (4:05).
MEDIA
Click image to the left for more content.
The Modern Periodic Table
In Mendeleev’s table, atomic mass increases from top to bottom of vertical columns, with successive columns going
left to right. Elements that are in the same horizontal row are groups of elements that were known to exhibit similar
chemical properties. However, even with the use of placeholders, there were some elements that did not quite fit
the pattern. For example, Mendeleev listed tellurium before iodine even though its atomic mass is higher, because
he knew that the properties of iodine were much more similar to those of fluorine (F), chlorine (Cl), and bromine
(Br) than they were to oxygen (O), sulfur (S), and selenium (Se). He simply assumed that there was an error in the
determination of one or both of the atomic masses. This turned out not to be the case, but Mendeleev was indeed
correct to group these two elements as he did.
Recall that Rutherford’s experiments leading to the discovery of the nucleus occurred in 1911, long after Mendeleev’s
periodic table was developed. Just two years later, in 1913, English physicist Henry Moseley (1887-1915) examined
the x-ray spectra of a number of chemical elements. His results led to the definition of atomic number as the number
of protons contained in the nucleus of each atom. He then realized that the elements of the periodic table should be
arranged in order of increasing atomic number instead of increasing atomic mass.
When ordered by atomic number, the discrepancies within Mendeleev’s table disappeared. Tellurium has an atomic
number of 52, while iodine has an atomic number of 53. Even though tellurium does indeed have a greater average
atomic mass than iodine, it is properly placed before iodine in the periodic table. Mendeleev and Moseley are
credited with formulating the modern periodic law, which states that when elements are arranged in order of
increasing atomic number, there is a periodic repetition of their chemical and physical properties. We will discuss
some of these chemical and physical properties later on in this chapter. The result is the periodic table as we know
it today.
Lesson Summary
• The early versions of the periodic table included approximately 60 known elements, while our current version
includes 118.
• An early version of the periodic table was first published by Julius Lothar Meyer in 1864, where he used the
concept of valence to group similar elements together.
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Chapter 1. History of the Periodic Table
• In 1865, Newlands described a periodic pattern in the properties of the elements that he referred to as the Law
of Octaves. This anticipated later developments in our understanding of the periodic law.
• Between 1869 and 1871, Russian chemist Dmitri Mendeleev systematically arranged 60 elements based on
increasing atomic weight.
• Mendeleev’s table became widely accepted, primarily because he predicted the characteristics and placement
of elements which were yet to be discovered.
• One of the major developments that allowed for what became known as the periodic table was the idea of
atomic mass, which is attributed to John Dalton.
• Characteristic properties of the elements could be related to atomic mass and atomic number.
• Ordering the elements by atomic number instead of atomic mass cleared up some of the discrepancies found
in older periodic tables and provided the basis for our current table of the elements.
Review Questions
1. Create a timeline that shows the contributions from the various scientists which led to the evolution of the
periodic table.
2. What were some of the limitations of the early versions of the periodic table?
3. What were some aspects of Mendeleev’s table that helped convince the scientific community to adopt its use?
4. How was Mendeleev’s table arranged? What was systematic about it?
5. What predictions did Mendeleev make with his table that were later confirmed?
6. What contributions did Moseley make to the modern periodic table?
7. The periodic table has evolved over time. Do you suppose it is a completed table at this point? In other words,
will it evolve further in the future?
Further Reading / Supplemental Links
• Barber, R. C., Karol, P. J., Nakahara, H., Vardaci, E., Vogt, E. W. (2011). Discovery of the elements with
atomic numbers greater than or equal to 113 (IUPAC Technical Report). Pure and Applied Chemistry, 83(7),
1485 - 1498.
• Bonifácio, V. D. B. (2012). QR-Coded Audio Periodic Table of the Elements: A Mobile-Learning Tool.
Journal of Chemical Education. doi: 10.1021/ed200541e
• Hsu, D. D. (2012). Chemicool Dictionary, from http://www.chemicool.com/dictionary.html
• Gorin, G. (1996). Mendeleev and Moseley: The Principal Discoverers of the Periodic Law. Journal of
Chemical Education, 73(6), 490. doi: 10.1021/ed073p490
• Trimble, R. F. (1981). Mendeleev’s discovery of the periodic law. Journal of Chemical Education, 58(1), 28.
doi: 10.1021/ed058p28
• van Spronsen, J. W. (1969). The priority conflict between Mendeleev and Meyer. Journal of Chemical
Education, 46(3), 136. doi: 10.1021/ed046p136
Points to Consider
• Even though the modern periodic table is a work in progress, there have been many other competing tables
which have not been widely accepted. Research different periodic tables and see how they describe the
periodic nature of the elements compared to the one with which we are most familiar.
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References
1. John Dalton. http://commons.wikimedia.org/wiki/File:Dalton%27s_Element_List.jpg . Public Domain
2. Dmitri Mendeleeev. http://commons.wikimedia.org/wiki/File:Mendelejevs_periodiska_system_1871.png .
Public Domain
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