1. CHEMISTRY
ATOMIC THEORY

2. Atomic Theory
Aristotle (300 BC) declares the existence of only 4 elements : fire,air, water and earth.
All matter is made up of these four element and matter had four properties : hot, cold, dry and wet.
Democritus (5BC) suggested all matter consists of very small, indivisible particles, named atomos (uncuttable or indivisible).

3. Arabic Scientists
When Feudalism reduced the demand for science in Europe, scolars fled to Arabic-Islamic lands.
Mathematics, Astonomy, Health and Medicine, Optics, and Chemistry flourished there during Europe’s Dark Ages.
Arabic-Islamic Scientists
Abu Al-Razi ( AD)
Ibn al-Haytham ( AD)
Abu Ibn-Sina ( AD)
Ibn Shatir ( AD)

4. Atomic Theory
1808, John Dalton, English, proposed precise definition of building block of nature, basis for modern era of chemistry.
Three main hypotheses :
* Law of definite proportions
* Law of multiple proportions
* Law of conservation of mass

5. Penemuan sinar-X Wilhelm Conrad Röntgen : penemu sinar-X
Bermulanya zaman fizik modern dan merevolusi kedoktoran diagnostik
Wilhelm Conrad Röntgen (27 March 1845 – 10 Februari 1923) ialah ahli fizik Jerman yang merupakan penerima pertama Penghargaan Nobel dalam Fizik, pada tahun 1901, untuk penemuannya pada sinar-X, yang menandai dimulainya zaman fizik modern dan merevolusi kedoktoran diagnostik.

6. Atomic Models
In the case of atoms, scientists use large models to explain somethings that is very small.
Models of the atom were used to explain data or facts that were gathered experimentally.
So,these models are also theories.

7. Models
Models are often used for things that are too small or too large to be observed or that are too difficult to be understood easily.

8. Democritus ( BC)
Universe was made of empty space and tiny bits of stuff
Called these tiny bits of stuff atomos
Atoms could not be divided.

9. Dalton (1808 AD) All elements are composed of indivisible particles
Atoms of the same elements are same
Atoms of different elements are different.
Compounds consisited of atoms of different elements combined together

10. Thomson (1900 AD) Plum pudding model
Atom made of a positively charged material with the negatively charged electrons scattered through it.

11. Rutherford (1911 AD) Mostly empty space Small, positive nucleus
Contained protons
Negative electrons scattered around the outside

12. Bohr (1913 AD)
Electrons move in definite orbits around the nucleus

13. The Electron Cloud Sometimes called the wave model
Spherical cloud of varying density
Varying density shows where an electron is more or less likely to be

14. The Structure of the Atom
Atom is the basic unit of an element that can enter into chemical combination.
Series of investigations conducted 1850’s till 20th century clearly demonstrated atoms made up of even smaller particles (subatomic particles), hence possess internal structure.

15. Structure of Atom

16. For more information :-
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