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A history of chemistry

A history of chemistry. “Old dead guys”. It all started back when…. 400 BC- Democritus- first to come up with the idea that things are made of “atoms”. Skip to. 1803- John Dalton Proposed the atomic theory. Next was. 1869- Dmitri Mendeleev

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A history of chemistry

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  1. A history of chemistry “Old dead guys”

  2. It all started back when… • 400 BC- Democritus- first to come up with the idea that things are made of “atoms”

  3. Skip to • 1803- John Dalton • Proposed the atomic theory

  4. Next was • 1869- Dmitri Mendeleev • Arranged elements into 7 groups with similar properties… 1st version of periodic table.

  5. 1897- JJ Thomson • Discovered electrons and isotopes

  6. 1909 Millikan • Famous experiment determined the charge of an electron… which is??

  7. 1911 Rutherford • Established that the nucleus of an atom was very dense and positively charged while electrons were outside the nucleus

  8. 1922 Niels Bohr • Made a model of the atom where electrons were in different orbitals

  9. 1932 Chadwick • Discovery of the neutron

  10. Moving on to atomic structure • First of all… Elements are substances that cannot be broken down into simpler parts • Elements are made of atoms.. .Carbon is made of carbon atoms etc. • How small is an atom??? • We can break down an atom but it loses its properties when we do…

  11. Atoms are made of… • Three types of particles • Electrons • Protons • Neutrons

  12. Electrons • Very tiny • Mass is basically zero (m=0) • Negative charge (-1) • Located flying around the nucleus

  13. Protons • Very large compared to electrons (mass =1) • Positive charge (+1) • Located in the nucleus of an atom

  14. Neutrons • Large like protons (mass=1) • Neutral charge or no charge • Located in the nucleus

  15. If this were the size of hydrogen nucleus, the electron would be spinning about a quarter mile away…. • In a neutral atom, protons always equal electrons • Hydrogen has… 1 proton… 1 electron • Helium has… 2 protons… 2 electrons

  16. Atomic number = number of protons in nucleus • Atomic Mass= how many protons AND neurtons • How many protons in H? • How many neutron in H • How many electrons?

  17. Let’s try another • How many P? N? E?

  18. P? N? E?

  19. Bohr Models • Hydrogen: • Helium:

  20. More Bohr Models • Boron • Neon (noble gas)

  21. Last one • Magnesium

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