1. Periodic Table

2. Mysteries of Matter http://www.pbs.org/program/mystery-matter/
Please note how Mendelev arranged the elements to form the periodic table we use today.

3. Johann Dobereiner– German
Found that Ca, Ba and Sr were very similar.
He noted that the atomic mass of strontium was about midway between the other two. He grouped these elements--- triads

4. “Triads” suggest an underlying pattern
Ca = Sr = Ba = 137
(40+137)/2 = 88.5
Cl = Br = I = 127
( )/2 = 81.2
K = Rb = Cs = 133
(39+133)/2 = 86
S = Se = Te = 125
(32+125)/2 = 78.5
Johann Döbereiner
Jena, Germany
1829
P = As = Sb = 122
(31+122)/2 = 76.5

5. John Newlands– 1863 English Chemist
He arranged the elements in order of their increasing atomic masses. He noted that there appeared to be a repetition of similar properties every eighth element. He placed seven elements in each group. He arranged the 49 elements known at that time into seven groups of seven each
Law of Octaves

7. 1869– Dmitri Mendeleev---Russian Chemist
Properties of the elements were a function of their atomic masses but that the similar properties occurred after periods that could vary in length. He placed seven elements in each of the first two periods and seventeen elements in the next two.

9. Mendeleev
Mendeleev had to leave some blank spots in order to group all the elements in the same column
To explain these blanks spots he suggested that there must be other elements to be discovered.
He predicted what properties and atomic masses that these would have and he was very close

12. Mendeleev’s Periodic Table
He arranged the elements by atomic mass

13. 1913 Henry Moseley Something was wrong with Mendeleev’s table
Te and I are in the wrong column if they are to be arranged by atomic mass
X-ray experiments showed that the nucleus of each element has an integral positive charge, the atomic number

14. Modern Periodic Table
The modern periodic table is now based on atomic number instead of atomic mass

15. Sir William Ramsey University College (London)
A new family of elements?!
Sir William Ramsey University College (London)
New gas
isolated from
the atmosphere!

16. A new column is needed for the new element!

17. Another gas discovered! (was originally seen in the sun)

18. Two more gases discovered!

19. Another gas discovered ! (Table needs to be restacked)

20. Niels Bohr
Copenhagen, Denmark

21. Glenn Seaborg Berkeley, California
1937
Only one left to be discovered!
1940
1939

22. Promethium was discovered in an atomic pile in Oak Ridge, Tennessee (1945)
And the transuranium elements were discovered by Seaborg and others

23. Periodic Trends
Radius Ionization Energy Electron Affinity Electronegativity

24. Relative Atomic Sizes Can Be Predicted by the Periodic Table
Atomic Size = Atomic Radius
Down a Group, Atomic Size Increases
Higher Primary Shells
Across a Period (lr), Atomic Size Decreases
Same Primary Shell
More Protons, More Electrons
The + Charge from p+ Pulls All e- In

25. Relative Atomic Sizes of the s- and p-Block Elements
Figure: 09-37
Title:
Relative atomic sizes of the representative elements
Caption:
Atomic size decreases as you move to the right across a period and increases as you move down a column in the periodic table.

26. Relative Ionization Energy Can Be Predicted from Periodic Table
Ionization Energy is the Energy Required to Remove One Electron from an Atom in the Gaseous State
X(g)  X+(g) + e-(g) First Ionization Energy
X+(g)  X2+(g) + e-(g) Second Ionization Energy...
Ionization Energy Increases Across a Period
Ionization Energy Decreases Down a Group
The attractive forces between the nucleus and electrons are tempered by distance.
Valence electrons are shielded from nucleus by all the core electrons.

27. Figure: 09-38
Title:
Ionization energy trends in the periodic table
Caption:
Ionization energy increases as you move to the right across a period and decreases as you move down a column in the periodic table.

28. Electronegativity
The Relative ability to attract electrons in a chemical bond

29. Octet Rule
Atoms tend to gain, lose or share electrons to acquire 8 valence electrons

30. Radius changes in the formation of ions
Cation--- Positively charged ion
Lose electrons, the radius gets smaller
Anion-- Negatively charged ion
Gain electrons, the radius gets larger