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ATOMS • Smallest particle of element • Same substance • From Greek word “Atomos” John Dalton • • • • • • Late 1700’s/1803 All substances are made of atoms Small particles cannot be divided Same elements atoms are alike Different elements atoms are different Atoms join together to make new substances JJ Thomson 1897 • • • • • • Small particles inside an atom Cathode-Ray Tube Experiment Negatively charged particles Atom is neutral Therefore positively charged particles Atom is + charged blob with electrons scattered Plum Pudding Model Ernest Rutherford 1909/1911 • Gold Foil Experiment • Atom mostly empty space • Light weight electrons move in empty space • Positively charged particles in very small, dense nucleus Gold Foil Expt. Niels Bohr 1913 • Electrons travel around nucleus in definite paths • Paths are energy levels • Electrons can jump from one level to another Bohr’s model Erwin Schrodinger: 1961 & Werner Heisenberg: 1976 The Wave Model Current/Modern Theory • Electrons do not travel definite paths • Exact path of electron cannot be predicted • Electrons are likely to in regions called electron clouds Electron cloud model Inside an Atom • • • • • Average diameter is 0.00000003 cm Subatomic particles: Protons are positively charged Electrons are negatively charged Neutrons are neutral/no charge Inside the Nucleus • Nucleus diameter is 1/100,000 of the atom • Location of protons and neutrons • Very dense – most massive yet very small volume • Isotopes – atoms with same # of protons but different # of neutrons The Subatomic Particles • • • • Atomic number is the number of protons Atom is neutral Number of protons = number of electrons Atomic mass = weighted average mass of protons & neutrons of isotopes • Mass number = sum of protons & neutrons The Subatomic Particles • Number of neutrons is equal to Atomic Mass minus Atomic number • Valence electrons are the electrons on the outermost energy level. • Electron Capacity for each energy level – 1st energy level: 2 electrons – 2nd energy level: 8 electrons – 3rd energy level: 8 electrons Forces in Atoms • Gravity – due to mass • Electromagnetic – same charges repel and different charges attract • Strong – force in the nucleus/ keep protons together • Weak – in radioactive atoms/ neutron can change into proton or electron Atom Puns 1. 2. 3. 4. 5. 6. A male member of the Ganese tribe Not Fat What doctors are for A 1 ton casket To press a shirt An amusing prisoner Atom Puns 7. Half of a dime 8. A policeman 9. A chemical Apache 10. The leg joint above the calf 11. He ______, I followed 12. What a torpedoed ship does 13. Mickey Mouse’s dog
