History of the Periodic Table

1. History of the Periodic
Table

2. The Modern Periodic Table of Elements

3. Origins of the Periodic Table
 Aristotle – four “roots”
 Earth, Air, Water, Fire
 Plato renamed the “roots” and called them elements
 The beginnings of the idea that there were only a
limited number of basic building blocks of all substances

4. The next 1500 years…
 The scientific world remained stagnant until the Age of
Enlightenment
 In 1649 Hennig Brand discovered P while trying to find the
Philosopher’s Stone
 This new substance could not be broken down into anything
more basic
 Questions began to be asked about the four elements and
what it really meant to be an element
 In 1661 Robert Boyle defined an element as “a substance that
cannot be broken down into a simpler substance by a
chemical reaction”

6. Antoine-Laurent de Lavoisier
 Wrote the first textbook on chemistry -
Traité Élémentaire de Chimie – in 1789
 Classified elements into four groups
 Elastic Fluids – light, caloric, O, N, H
 Nonmetals – S, P, C, HCl, HF, H3BO3
 Metals – Sb, As, Ag, Bi, Co, Cu, Sn, Fe,
Mn, Hg, Mo, Ni, Au, Pt, Pb, W, Zn
 Earths – lime, MgO, BaO, SiO2
 While Lavoisier classified elements,
there was no organization to his table
based on properties of the elements.

8. Johann Wolfgang Döbereiner
 In 1817, Döbereiner began the first attempt to classify
and list the elements based on certain properties.
 He organized sets of 3, or triads of, elements in which
the atomic mass of the middle element was the average
of the other two.
 This was the first hint at the groups we see in the
modern table.

9. Classification of Elements
 In 1862, Alexandre-Emile Béguyer de Chancourtois, a
French geologist devised a complicated way of arranging
the elements around a cylinder that correctly predicted
periodicity
 In 1865, John Newlands identified what he called the
“Law of Octaves” according to which elements behaved
much like musical notes and repeated a pattern with
every octet
 By 1869, 63 separate elements had been identified, and
trends were beginning to be noticed

11. Dimitri Mendeleev
 Mendeleev was a Russian chemist
 He arranged the elements according to atomic mass and
discovered that if listed in rows and columns certain
trends became clear.
 Elements with similar properties either have atomic
masses that are nearly equal (elements which are side
by side - Pt, Ir, Os) or increase in a certain increment
(elements which are in a single column – K, Rb, Cs)
 With his table, Mendeleev was able to accurately
predict undiscovered elements and their properties

12. Henry Moseley
 In 1914, Moseley, a British scientist, began performing
experiments on elements to better understand their
atomic structure
 He found that different elements responded differently
to bombardment with x-rays and that they each had a
unique frequency
 That frequency corresponded to the number of protons
in the atom.
 Introduced atomic number (Z)

13. Glenn Seaborg
 During research related to the Manhattan Project,
Seaborg proposed a change to Mendeleev’s structure.
 The series of 14 elements following Actinium and
Lanthanum were left out of Mendeleev’s table because
they really didn’t fit.
 Seaborg proposed that they belong to their own series
due to their atomic/electronic structure (f orbitals)