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”
5.
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.
7.
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
10.
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)
Editor's Notes
Grey – before 1800
Blue-green – 1800-1849
Dark purple – 1850-1899
Purple – 1900-1949
Light purple – 1950-1999
