Chapter 8 Notes - Chapter 8 Notes Atoms and Periodic...

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Chapter 8 Notes Atoms and Periodic Properties Orbit vs. orbital : orbit is based on classical chemical structure where electrons move around the nucleus , orbital is based on probability distribution. Atomic structure discovered Seaborgue – new element that is the first to be named after someone who is still alive. Ancient Greek: Plato and Aristotle: reasoned that there is no limit to how much you can break down. They thought that matter is continuously and infinitely divisible (prevailing argument). Democritus (460-362 BC): reasoned that there is the smallest particle known as the atom ( first to say the word atom ) that cannot be broken down. Matter consists of indivisible particles called “atoms.” He was taught by Plato and Aristotle. John Dalton (early 1800’s): Used atomic theory to explain chemical reactions. He began Atomic Theory Dalton’s Atomic Theory: All matter consists of indivisible particles called atoms Atoms of the same elements are identical and atoms of different elements are different Chemical compounds are made of atoms in specific integer ratios Atoms are neither created nor destroyed in chemical reactions Discovery of the electron Cathode Rays – the negative charged beam was seen to come from the cathode end of a tube when a shadow is seen on the other end – they are negative cause they became attracted to the positive magnetitic plate – and they have mass because he measured it with a pinwheel. J.J. Thomson (late 1800’s) Performed cathode ray experiment He did not determine the charge, he did not determine the charge, but he determined the mass to charge ratio Discovered negatively charged electrons Measured electron’s charge-to-mass ratio Identified electron as a fundamental particle Thomson discovered electron and determined charge to mass ratio. q/m = 1.7584 X 10^11 C/kg Robert Millikan (1906) He discovered the charge of an electron He used the oil drop experiement Charge on droplets = multiples of electron charge Charge + Thomson’s result gave electron mass Millikan determined the charge of the electron in a value as a constant number
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He determined the charge of an electron, but simply calculated the mass from the work of Thomson and his own. Using his constant and Thomson’s work, mass could be calculated. m = q/1.7584 X 10^11 = (he discovered q, q = 1.6 X10^-19) 9.11 X10^-31kg Early Models of the atom Thomson’s “Plum pudding” model Electrons are embedded in blob of positively charged matter like “raisins in plum pudding” Ernest Rutherford (1907) Scattered alpha particles off gold foil Most passed through without deflection, a few were deflected and a few were reflected. Conclusion: an atom must have a positive charge in a small,
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Chapter 8 Notes - Chapter 8 Notes Atoms and Periodic...

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