1. Development of the Periodic Table
1.1.2 History of Chemistry
Development of the
Periodic Table

2. History of the idea of Elements

3. First contact Fire Started by lightning
Started by physical means - rubbing sticks or banging flints but it is a chemical reaction
Allowed man to colonise other colder areas

4. Getting better Bronze A mixture of copper and tin
Both can be found native
Mixture has properties not intermediate between both
Bronze is much harder than either copper or tin
Still not real chemistry

5. The real McCoy Iron extracted from ores by smelting
Heating ore with charcoal
Reduced the oxide [ removed oxygen] to the metal
2 Fe2O3 + 3 C = 4 Fe + 3 CO2 ore
First happened about 1000 BC

6. Ancient Greeks I Thought everything composed of four elements Earth
Air [wind]
Fire
Water

7. Ancient Greeks II Democritus Came up with the idea of atoms
Break up a piece of matter into two
Take one half and break it into two
eventually you wont be able to divide it any more even in your imagination
indivisible
Atomos in Greek

8. Ancient Greeks III Silver
Gold
Mercury
Sulphur
Carbon
Lead
Tin
Copper
Iron
They knew some real elements but did not realise it
With the exception of Iron these can be found native although many of them are more common as ores
- i.e. combined with other elements from which they must be separated

9. Dark Ages Not much happening [Dark Ages] Alchemists
Trying to find two things
(i) The Elixir of Life for eternal youth
(ii) Touchstone
turns base metals
[lead or iron] into gold
Phosphorous
Discovered
Sulphuric Acid
Hydrochloric Acid
Distillation

10. Robert Boyle 1661 Earl of Meath Boyles [Gas] Law
Elements cannot be broken down into anything simpler

11. Lavoisier 1790 Made a list of elements known at time 22 of them
plus some things that some said were elements and others said were not
Discovered oxygen??

12. Davy Date 1778 - 1829 Discovered laughing gas
used as anaesthetic - much later
Discovered electrolysis using a voltaic pile
Electrolysis is a Chemical reaction caused by electric current.
Water gives H2 and O2
Used electrolysis to find many elements
K [1807], Na, Ca, Ba, Sr and Mg

13. Dalton
1808
Atomic Theory
All matter made up of very small particles called atoms
They cannot be broken down into anything simpler [by chemical means]

14. Dalton also used some of the Greek symbols

15. Greek symbols some used by Dalton e.g. silver and gold

16. Periodic Table begins to appear

17. Periodic Table
People began to arrange elements into groups in all sorts of ways
Weight [Relative Atomic Mass] was one of the easiest ways to arrange them
Led to some elements being misplaced e.g. Te / I

18. Now it is a list of elements arranged so as to demonstrate trends in their
Physical properties and
Chemical properties

19. Dobereiner [1780-1849] Ca / Sr / Ba Cl / Br / I Li / Na / K
People grouping things together and arranging them
groups of 3 similar elements where the middle one is intermediate
called them triads
Ca / Sr / Ba
Cl / Br / I
Li / Na / K

20. Newlands
Tried to find some mathematical relation between the atomic weights of elements which were chemically similar
Groups called octaves
Arranged the elements in rows of seven
Eighth element had properties similar to the first

21. “Law of Octaves” because of its similarity to musical octavesK
Ca ? ? As Se Br
Na Mg Al Si P S Cl Li
Be B C N O F

22. Newlands 1863 Law of Octaves Listed known elements - 60
Arranged in order of atomic mass
Properties repeat every eighth element
Noble gases not known at time

23. Mendeleev 1869 Arranged elements according to weight and properties
so they would fit into their property space rather than only weight
Te / I Meedeleev assumed weight wrong - they were not but weight is not a basic property
Left gaps for elements yet to be discovered

24. Predicted the properties of the missing elements and their compounds accurately
Within 16 years 3 gaps filled by Sc, Ga and Ge
Still no Noble Gases
He 1868 Ar 1894 Ne, Kr and Xe in 1898 Rn 1900

25. Mendeleev’ s Table

26. Henry Mosely
Measured No.of protons in the nuclei of atoms. Atomic number to arrange elements.

27. Moseley Arrangement by Atomic Number rather than by Atomic Mass
Mendeleev was right placing Te before Iodine
Final step in Periodic Table

28. Modern periodic table

29. Mendeleev’s v. Modern Table
Modern Periodic Table
Arranged by atomic number
More elements in modern – Noble Gases
No gaps – Mendeleev left gaps to make elements fit into proper column – In a few cases reversed the order of elements so the fitted into groups with similar properties
Transition elements in a separate block