Powerpoint presentation on an Atom
- 2. Smallest possible unit into which matter can be divided, while still maintaining its properties. Made up of: Protons neutrons electrons The solar system is commonly used as an analogy to describe the structure of an atom + + + +
- 3. J.J Thomson1897 in discovered the electron. In 1909 Rutherford done gold foil experiment and proposed new atomic model. In 1912 Neil Bohr proposed new atomic model that explained arrangement of electrons in an atom
- 4. THOMSON’S ATOMIC MODEL According to Thomson's model of atom electrons are embedded uniformly in a positively charged sphere. An atom is neutral as positive and negative charge is equal in magnitude
- 5. DRAW BACKS OF ATOMIC MODEL OF JJ .THOMSON It could not explain the result of the experiments carried out other scientists like Rutherford
- 6. RUTHERFORD’S EXPERIMENT A great scientists Rutherford carried out an experiment in which he took an gold foil which was only 1000 atoms thick He allowed alpha () particles to strike the gold foil in vacuum
- 8. OBSERVATIONS Most of the () particles pass straight through gold foil A few () particles are deflected through small angles A very few () particles completely rebound on hitting the gold foil
- 9. RUTHERFORD’S ATOMIC MODEL 1) There is a positively charged nucleus in centre of atom. 2) Most of the space in atom is empty. 3) Almost entire mass of atom is in nucleus. 4) Electrostatic attraction b/w (+ve) charged nucleus and (-ve) charged electrons hold atom together 5) Electrons follow a spiral path around the nucleus
- 10. Draw Back of atomic model of Rutherford
- 11. BOHR’S ATOMIC MODEL To over come the drawbacks of the atomic model of Rutherford , Neil-Bohr gave the new arrangement of electrons . When a electron looses energy ,it jump to lower shell. When a electron gains energy ,it jump to higher shell. When an electron is in a particular shell , it doesn’t loose or gain energy Electrons could revolve around the nucleus in only “certain orbits”(Each having variable radius)
- 12. BOHR-BURY SCHEME According to Neil-Bohr’s atomic model the maximum no. of electrons which can be accommodated in particular shell is numerically equal to 2n2 Where n = the shell no.(energy level)
- 13. Hydrogen (H) Atom • Notice the one electron in the first orbit Even though there are no neutrons present, Hydrogen is still considered an atom How many more electrons can fit in the 1st orbit/ level? + + - = 1 = 0 = 1
- 14. Oxygen (O) Atom • Notice the two electrons in the first orbital/level and the six in the second How many more electrons can fit in the 2nd orbit/ level? + + + - = 8 = 8 = 8
- 15. Sodium (Na) Atom • Notice the two electrons in the first orbit/level, eight in the second, and one in the third + - = 11 = 12 = 11 How many more electrons can fit in the 3rd orbit/ level? + +