CHEMISTRY ATOMIC THEORY

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).

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 (865-925 AD) Ibn al-Haytham (965-1039 AD) Abu Ibn-Sina (973-1037 AD) Ibn Shatir (1305-1375 AD)

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

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.

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.

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.

Democritus (470-375 BC) Universe was made of empty space and tiny bits of stuff Called these tiny bits of stuff atomos Atoms could not be divided.

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

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

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

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

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

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.

Structure of Atom

For more information :- www.visionlearning.com www.wikipedia.org/wiki/Atomic_theory http://www.youtube.com/watch?v=6p5nEh Dv-cE