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Published byChristiana Mathews Modified over 8 years ago
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Atomic Structure
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Smallest particle of an element w/ properties of that element About 90 natural elements Combine to form compounds ◦ Atoms elements compounds
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460 – 370 BC: Democritus ◦ “atomos” (indivisible & indestructible) ◦ Greeks believed in 4 basic elements ◦ Accepted for 2000 years
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Law of Conservation of Matter ◦ Matter is neither created nor destroyed
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Law of Definite Proportions ◦ A compound always contains elements in a certain, definite proportion & no other combinations ◦ Ex. H2OH2O CO HCl
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Law of Multiple Proportions ◦ Elements may combine in more than one proportion forming different compounds ◦ Led to the atomic theory 1. all matter is composed of atoms which are indivisible 2. all atoms of the same element are alike, atoms of different elements are different
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3. Compounds are formed when atoms of different elements combined in fixed proportions 4. Chemical reactions involve a rearrangement of atoms Model:
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Discovers proton using cathode ray tube & noticing that rays traveled in opposite direction of cathode (-) Mass is 1840x’s that of an electron
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Discovered electron using cathode ray tube where flow goes from cathode (-) to anode (+) Millikan in 1916 found mass(1/1840 x’s mass of H atom) & charge(-1) Model:
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Discovers a condensed core w/ gold foil experiment Called it the ‘nucleus’ & composed of protons & neutrons Model known as “Nuclear Atom” Model:
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Discovers subatomic particle w/ no charge aka Neutron Mass nearly equal to proton (slightly larger)
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Protons ◦ Positive ◦ In nucleus ◦ Mass = 1840 x’s an electron ◦ Same as atomic # Electrons ◦ Negative ◦ Outside nucleus ◦ 1/1840 mass of proton Neutrons ◦ Neutral ◦ In nucleus ◦ Almost the same as proton, slightly larger
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Mass # = #protons + # neutrons Mass # for element & # neutrons may vary Ex. ◦ 14 C 6 p +, 8n o ◦ 12 C 6 p +, 6n o
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Increase/decrease in # of electrons In atom: ◦ Protons = electrons Ex. Na ◦ 11p +, 11e - Na + ◦ 11p +, 10e -
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Found using mass spectrometer Based on average of relative abundance of isotopes of the element Measured in amu’s (1/12 of a carbon atom)
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Number of stable isotopes % of each isotope Mass of each isotope
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