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Elements, Atoms and Ions

Elements, Atoms and Ions. Chapter 3. All Matter can be broken into “elements” 114 elements (as of this morning) 88 natural elements 9 elements make up 98% of the Earth’s mass (see page 48) Elements are represented by “symbols” One or two letter shorthand (first letter is capital)

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Elements, Atoms and Ions

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  1. Elements, Atoms and Ions Chapter 3

  2. All Matter can be broken into “elements” • 114 elements (as of this morning) • 88 natural elements • 9 elements make up 98% of the Earth’s mass (see page 48) • Elements are represented by “symbols” • One or two letter shorthand (first letter is capital) • Universally recognized Al • Oxygen O • Nitrogen N • Cobalt Co • Potassium K • Antimony Sb • Tungsten W Potassium Lead Antimony

  3. Atomos Early History of the Atom • Democritus (400 BC) • Greek philosopher  not a scientist • Suggested that the world was empty space and “atoms” • Proposed an atom for every type of material (gold, wood, fire…)

  4. Aristotle (350 BC) • Said that matter was “continuous” it can be divided into infinitely small pieces • Accepted until the 17th century

  5. Modern History of the Atom • John Dalton (early 1800’s) • First Modern Atomic Model • Elements are made up of atoms. • Atoms of the same element are the same. • Atoms of different elements are different. • Different types of atoms combine to make compounds. Compounds always have the same relative numbers and types of atoms. • In chemical changes, atoms cannot be created or destroyed. KOH + HCl  H2O + KCl

  6. Antoine Lavoisier • Work was studied (ripped off) by Dalton • Law of Conservation of Mass In a normal chemical reaction, matter cannot be created or destroyed. A burning candle will get smaller and lose mass. When the candle is burned in an enclosed container, the total mass of the system does not change.

  7. Electrical Current Glass Cathode Ray Tube • JJ Thomson (1890’s) • Observed “Cathode Rays” • Streaks of light went from the negative cathode to the positive anode ∴ Cathode Rays are negative Cathode (-) Anode (+)

  8. Electrical Current N S • Streaks of light were deflected by a magnet ∴Cathode Rays are Matter • Cathode Rays = Electrons

  9. - - - - - - • “Plum Pudding” Model • Electrons are stuck into a positive mass • When energy is added, the electrons are ripped free + + + + + + + + + + +

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