Chapter 5

History of
the
Periodic
Chapter 5
History of the Periodic
Table

The Periodic Law –
Physical and
Chemical
Properties of
Elements are
Periodic Functions
History of the Periodic
Table

The Periodic Law –
Physical and
Chemical
Properties of
Elements are
Periodic Functions
The development of the
periodic table begins
with German chemist
Johann Dobereiner
(1780-1849) who
grouped elements based
...
Calcium (atomic mass 40),
strontium (atomic mass 88),
and barium (atomic mass 137)
possess similar chemical
properties.

(...
Dobereiner noticed the
atomic mass of strontium fell
midway between the masses
of calcium and barium:
Ca Sr
Ba
40
?? 137
(...
Dobereiner noticed the
same pattern for the alkali
metal triad (Li/Na/K) and
the halogen triad (Cl/Br/I).
Li Na K
Cl Br I
...
(Was this merely a
coincidence or did
some pattern to the
arrangement of the
elements exist?)
1829 Dobereiner proposed
the
Law of Triads:
The middle element in the
triad had atomic mass that
was the average of the ot...
1829 Dobereiner proposed
the
Law of Triads:
The middle element in the
triad had atomic mass that
was the average of the ot...
(Soon other scientists found
chemical relationships extended
beyond triads. Fluorine was added
to Cl/Br/I group; sulfur, o...
First International
Congress of Chemists
Karlsruhe, Germany 1860
-to discuss uniform ways to
measure Atomic Mass and to
so...
First International
Congress of Chemists
Karlsruhe, Germany 1860
-to discuss uniform ways to
measure Atomic Mass and to
so...
Demetri Mendeleev 1869
FATHER OF THE
MODERN PERIODIC TABLE

Mendeleev insisted on
ordering elements by
atomic mass, and
gr...
Demetri Mendeleev 1869
FATHER OF THE
MODERN PERIODIC TABLE

Mendeleev insisted on
ordering elements by
atomic mass, and
gr...
Demetri Mendeleev 1869
FATHER OF THE
MODERN PERIODIC TABLE

Mendeleev insisted on
ordering elements by
atomic mass, and
gr...
This resulted in several
"gaps" in the Periodic
Table. Both Gallium (Ga)
and Germanium (Ge)
were unknown at the time
Thus ...
Mendeleev concluded
therefore that there
must be two elements,
which he called
"eka-Aluminum" and
"eka-Silicon" which
must...
Mendeleev made
predictions on
some of the vacant
spaces in the
Periodic Table.
Such as:
Eka-silicon, (Germainium)
Eka-alum...
Gallium was
discovered in 1875
by Paul Emile.
Its general
chemistry
matched
Mendeleev's
predictions for
Germanium (ekasilicon) was discovered in
1886 by Clemens Winkler.
The agreement with Mendeleev's
predictions are shown in ...
Henry Moseley 1913
Assistant to Rutherford
(killed at Gallipoli at age 28)

-discovered a mathematical
relationship betwee...
Henry Moseley 1913
Assistant to Rutherford
(killed at Gallipoli at age 28)

-discovered a mathematical
relationship betwee...
He noticed that when
struck by the cathode
rays, different metals
gave off x-rays with
distinct wavelengths.
Moseley realized that the
atomic numbers were not just a
convenient numbering scheme
for the elements, but had a real
phys...
Law of Octaves (1837-1898),
English chemist John Newlands
having arranged the 62 known
elements in order of increasing ato...
Newlands was the first to
formulate the concept of
periodicity in the properties of the
chemical elements.
In 1863 he wrot...
Noble Gases
1864 He discovered on the Sun
1894 Englishman John Williams Strutt
(Lord Rayleigh) and Scottish Sir
William Ra...
Ch 5 Notes Part 1
Ch 5 Notes Part 1
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Ch 5 Notes Part 1

  1. 1. Chapter 5 History of the Periodic
  2. 2. Chapter 5
  3. 3. History of the Periodic Table The Periodic Law – Physical and Chemical Properties of Elements are Periodic Functions
  4. 4. History of the Periodic Table The Periodic Law – Physical and Chemical Properties of Elements are Periodic Functions
  5. 5. The development of the periodic table begins with German chemist Johann Dobereiner (1780-1849) who grouped elements based on similarities.
  6. 6. Calcium (atomic mass 40), strontium (atomic mass 88), and barium (atomic mass 137) possess similar chemical properties. (Find them on the Periodic Table)
  7. 7. Dobereiner noticed the atomic mass of strontium fell midway between the masses of calcium and barium: Ca Sr Ba 40 ?? 137 (40 + 137) ÷ 2 = ??
  8. 8. Dobereiner noticed the same pattern for the alkali metal triad (Li/Na/K) and the halogen triad (Cl/Br/I). Li Na K Cl Br I 7 ?? 39 35 ?? 127
  9. 9. (Was this merely a coincidence or did some pattern to the arrangement of the elements exist?)
  10. 10. 1829 Dobereiner proposed the Law of Triads: The middle element in the triad had atomic mass that was the average of the other two members.
  11. 11. 1829 Dobereiner proposed the Law of Triads: The middle element in the triad had atomic mass that was the average of the other two members.
  12. 12. (Soon other scientists found chemical relationships extended beyond triads. Fluorine was added to Cl/Br/I group; sulfur, oxygen, selenium and tellurium were grouped into a family; nitrogen, phosphorus, arsenic, antimony, and bismuth were classified as another group.)
  13. 13. First International Congress of Chemists Karlsruhe, Germany 1860 -to discuss uniform ways to measure Atomic Mass and to solve other communication problems. -Only 60 Elements at this time
  14. 14. First International Congress of Chemists Karlsruhe, Germany 1860 -to discuss uniform ways to measure Atomic Mass and to solve other communication problems. -Only 60 Elements at this time
  15. 15. Demetri Mendeleev 1869 FATHER OF THE MODERN PERIODIC TABLE Mendeleev insisted on ordering elements by atomic mass, and grouping them by their PROPERTIES.
  16. 16. Demetri Mendeleev 1869 FATHER OF THE MODERN PERIODIC TABLE Mendeleev insisted on ordering elements by atomic mass, and grouping them by their PROPERTIES.
  17. 17. Demetri Mendeleev 1869 FATHER OF THE MODERN PERIODIC TABLE Mendeleev insisted on ordering elements by atomic mass, and grouping them by their PROPERTIES.
  18. 18. This resulted in several "gaps" in the Periodic Table. Both Gallium (Ga) and Germanium (Ge) were unknown at the time Thus there was a gap under Aluminum (Al) and a gap under Silicon (Si)
  19. 19. Mendeleev concluded therefore that there must be two elements, which he called "eka-Aluminum" and "eka-Silicon" which must fill these gaps
  20. 20. Mendeleev made predictions on some of the vacant spaces in the Periodic Table. Such as: Eka-silicon, (Germainium) Eka-aluminium, (Gallium)
  21. 21. Gallium was discovered in 1875 by Paul Emile. Its general chemistry matched Mendeleev's predictions for
  22. 22. Germanium (ekasilicon) was discovered in 1886 by Clemens Winkler. The agreement with Mendeleev's predictions are shown in the table below Property Ekasilicon Germanium 72 72.32 Density (g/cc) 5.5 5.47 Atomic volume 13 13.22 Atomic Mass Outer Shell Electrons (Dots) Boiling point of GeCl4 /degrees Celsius 4 4 <100 86
  23. 23. Henry Moseley 1913 Assistant to Rutherford (killed at Gallipoli at age 28) -discovered a mathematical relationship between the frequency of X-rays and the atomic number.
  24. 24. Henry Moseley 1913 Assistant to Rutherford (killed at Gallipoli at age 28) -discovered a mathematical relationship between the frequency of X-rays and the atomic number.
  25. 25. He noticed that when struck by the cathode rays, different metals gave off x-rays with distinct wavelengths.
  26. 26. Moseley realized that the atomic numbers were not just a convenient numbering scheme for the elements, but had a real physical meaning - ultimately realized as being the number of protons (and electrons) in an (neutral) element
  27. 27. Law of Octaves (1837-1898), English chemist John Newlands having arranged the 62 known elements in order of increasing atomic masses, noted that at in intervals of eight, elements had similar physical/chemical properties.
  28. 28. Newlands was the first to formulate the concept of periodicity in the properties of the chemical elements. In 1863 he wrote a paper proposing The Law of Octaves: Elements exhibit similar behavior to the eighth element following it in the table.
  29. 29. Noble Gases 1864 He discovered on the Sun 1894 Englishman John Williams Strutt (Lord Rayleigh) and Scottish Sir William Ramsey discovered Argon 1895 He discovered on Earth 1898 Krypton and Xenon-Ramsey 1900 Radon discovered by German Friedrich Ernst Dorn

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