1. EVIDENCE THAT LED TO THE MODIFICATION OF DALTON’S ATOMIC THEORY DALTON’S ATOMIC THEORY : Matter consists of small paricles called atoms. All elements are made up of atoms Atomos are indivisible and indistructable Atoms of a given element are identical in mass and in all other properties A compound is formed when the atoms of two or more elements combine

2. Dalton's atomic theory is correct in essence with a few exceptions to his rules: 1) Atoms are the smallest unit of mater that retain the physical and chemical properties of an element, however they ARE DIVISIBLE BY NON-CHEMICAL MEANS. 2) All atoms of a single element contain the the identical number of protons and electrons, however their masses may vary with the number of neutrons in different isotopes (some of which are unstable and decay).but for very basic purposes, Dalton's theory holds true. These assumption were proven to be inaccurate by the experiments and theories of J.J thompson , By defflecting cathode rays with both electric and magnetic fields he proved the existence of the electron.Thereofore, his worked made it apparent that atoms were not invisible and it gave evidence of the existence of subatomic particles.

3. The proton was then discoverded by Goldstein in 1900 after observing the rays in a cathode ray tube that travelled in the direction opposite to that of cathode rays. However, in 1913 Mosley suggested the idea of the neutron but it was in 1932 that James Chadwick bombarded the element Be with alpha particles .This experiment helped him to detect the suggested neuton. In 1903 another of Dalton’s threory was proven to be incorrect as Henri Bacquerel discovered radioactivity where elements of the same element did not have the same mass. Dalton’ s atomic theory provided the foundation on which other scientists have built on.

4. IN 1897 J.J T carried out an experiment in which he defflected cathode rays using both magnetic and electric fields.From the experiment he realised that the beam of paricles were negatively charged and extremely light in mass. His experiment proved that atoms were not invisible and it proved the existence of subatomic particles.Thomson proposed the plum pudding model of the atom in which the negatively charge particles were embedded in a shere of positive charge. j.Jthompson

5. EUGEN GOLDSTEIN Eugen Goldstein (September 5, 1850 – December 26, 1930) was a German physicist who is credited with the dicovery of the proton. He discovered the proton with the help of discharge tube with a perforated Cathode when he discovered that the rays in a cathode ray tube were travelling in the direction opposite to that of cathode rays. Goldstein thought that since the atom was defined as being electrically neutral that they must contain an equal number of positive charge particles as the negatively chaarged particles.

6. RUTHERFORD The Rutherford model or planetary model is a model of the atom devised by Ernest Rutherford. Rutherford directed the famous Geiger-Marsden experiment in 1909, which suggested on Rutherford's 1911 analysis that the so-called "plum pudding model"ofJ. J. Thomson of the atom was incorrect. In 1909, rutherfofrd ‘s colleagues geiger and marsden bombarded thin metal foils with alphe particles to test thompson’s model of the atom .

7. Rutherford expected all of the particles to be deflected just a bit as they passed through the plum pudding. He found that most of the a’s he shot at the foil were not deflected at all. They passed through the foil and emerged undisturbed. Occasionally, however, particles were scattered at huge angles. While most of the a’s were undisturbed, a few of them bounced back directly.

9. NEILS BOHR The Bohr model, introduced by Niels Bohr in 1913, depicts the atom as a small, positively charged nucleus surrounded by electrons that trave He suggested that electrons could only have certain classicalmotions. The electrons can only travel in certain orbits: at a certain discrete set of distances from the nucleus with specific energies. The electrons of an atom revolve around the nucleus in orbits. These orbits are associated with definite energies and are also called energy shells or energy levels. Therefore, the electrons do not continuously lose energy as they travel in a particular orbit. They can only gain and lose energy by jumping from one allowed orbit to another, absorbing or emitting electromagnetic radiation with a frequency ν determined by the energy difference of the levels according to the Planck relation.

10. HENRY MOSLEY Moseley redefined the idea of atomic numbers into a real and objective whole-number quantity that was experimentally measurable. Moseley's law provided a reasonably complete experimental set of data that supported the atom, with a positively-charged nucleus surrounded by negatively-charged electrons in which the atomic number is understood to be the exactly physical number of positive charges (later discovered and called protons) in the central atomic nuclei of the elements.

11. JAMES CHADWICK In1932, James Chadwick proved that the atomic nucleus contained a neutral particle which had been proposed more than a decade earlier by Ernest Rutherford. He did this by bombarding the element Be with alpha particles which causes it to emit this mysterious radiation.It was discovered that this radiation, upon striking a proton-rich surface (paraffin was the preferred example), would discharge some of the protons, which could then be detected using a Geiger counter (a device that measures radiation).As a result the particles had passed through solid lead and they were neither defflected by the electric or magnetic fields.Hence,he had detected the neutron .

12. The quest for a systematic arrangement of the elements started with the discovery of individual elements. By 1860 about 60 elements were known and a method was needed for organization. Many scientists made significant contributions that eventually enabled Mendeleev to construct his table. The periodic table did not end with Mendeleev but continued to take shape for the next 75 years.

13. Debereiner’s Law Of Trials The development of the periodic table begins with German chemist Johann Dobereiner (1780-1849) who grouped elements based on similarities. Calcium (atomic weight 40), strontium (atomic weight 88), and barium (atomic weight 137) possess similar chemical prepares. Dobereiner noticed the atomic weight of strontium fell midway between the weights of calcium and barium:

14. In 1829 Dobereiner proposed the Law of Triads: Middle element in the triad had atomic weight that was the average of the other two members. 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. First Periodic Table It was a 19th century geologist who first recognized periodicity in the physical properties of the elements. AlexandreBeguyer de Chancourtois (1820-1886), published in 1862 a list of all the known elements. Using geological terms and published without the diagram, de Chancourtois ideas were completely ignored until the work of Mendeleev.

15. Law of Octaves After arranging 62 known elements in order of increasing weights John Newlands noticed that at intervals of 8 elements similar chemical / physical properties reappear

16. Mendeleev's Periodic Table In 1869, Russian chemist Dimitri Mendeleev (1834-1907) proposed arranging elements by atomic weights and properties. Mendeleev's periodic table of 1869 contained 17 columns with two partial periods of seven elements each In 1871 Mendeleev revised the 17-group table with eight columns (the eighth group consisted of transition elementsMendeleev predicted the discovery of new elements.

18. NOBLE GASES LordRrayleigh and William Ramsey discovered the inert gases. after discovering argon in 1895 the other inert gases were positioned on the periodic table on discovery. the periodic table was taking shape with elements were arranged by atomic weight.

19. Moseley's Periodic Law When Moseley arranged the elements according to increasing atomic numbers and not atomic masses, some of the inconsistencies associated with Mendeleev's table were eliminated. The modern periodic table is based on Moseley's Periodic Law (atomic numbers).

21. Modern Periodic Table The last major change to the periodic table resulted from Glenn Seaborg'swork in the middle of the 20th century. Seaborg discovered transuranium elements 94 to 102 .

22. WILDLIFE . The greatest threat is to future generations of sea creatures; the radiation could interfere with reproduction and the development of young, causing a collapse of the population

23. Because of saltwater corrosion problems and pipes clogging by salt, fresh cooling water is transported by barge to Fukushima. Satellite image on 16 March of the four damaged reactor buildings

24. Satellite image on 16 March of the four damaged reactor buildings Because of saltwater corrosion problems and pipes clogging by salt, fresh cooling water is transported by barge to Fukushima.

25. RADIOACTIVITY Radioactivity is a part of our earth - it has existed all along. Naturally occurring radioactive materials are present in its crust, the floors and walls of our homes, schools, or offices and in the food we eat and drink. There are radioactive gases in the air we breathe. Our own bodies - muscles, bones, and tissue - contain naturally occurring radioactive elements. The effects of radiation at high doses and dose rates are reasonably well documented. A very large dose delivered to the whole body over a short time will result in the death of the exposed person within days

26. EFFECTS OF RADIOACTIVITY RADIOACTIVITY IN JAPEN The radiation effects from the Fukushima Daiichi nuclear disaster are the results of release of radioactive isotopes from the crippled Fukushima Daiichi Nuclear Power Plant after the 2011 Tōhoku earthquake and tsunami. Radioactive material has been released from the Fukushima containment vessels as the result of deliberate venting to reduce gaseous pressure, deliberate discharge of coolant water into the sea, and accidental or uncontrolled events. Water levels dropped precipitously Monday inside a stricken Japanese nuclear reactor, twice leaving the uranium fuel rods completely exposed and raising the threat of a meltdown, hours after a hydrogen explosion tore through the building housing a different reactor.