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Honors Chemistry Chapter 4

Honors Chemistry Chapter 4. The Structure of the Atom. Early Theories of Matter. Atomic Theory Democritus Dalton. Dalton’s Atomic Theory. Based on experimental results Matter consists of atoms All the atoms of an element are alike

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Honors Chemistry Chapter 4

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  1. Honors Chemistry Chapter 4 The Structure of the Atom

  2. Early Theories of Matter • Atomic Theory • Democritus • Dalton

  3. Dalton’s Atomic Theory • Based on experimental results • Matter consists of atoms • All the atoms of an element are alike • Atoms of one element differ from atoms of other elements • Atoms are indestructible and only rearranged during chemical reactions

  4. Atoms can combine in simple, whole-number ratios to form compounds • Pg. 102

  5. Discovery of the electron • Cathode ray tube (Crooke’s tube) • Pg. 105 picture • Cathode rays • Particles with negative charge

  6. JJ Thompson • Used cathode ray tube to determine charge/mass ratio of particles • Identified the particles as electrons

  7. Robert Millikan • Calculated the charge and mass of an electron • “Oil drop” experiment • Electron carries exactly one unit of negative charge • Mass is 1/1840 the mass of a hydrogen atom

  8. Each electron carries one unit of negative charge • Proposed “plum pudding” model of the atom • “chocolate chip cookie” model • Electrons stuck in positive “dough”

  9. Rutherford’s Gold Foil Experiment • pg. 107

  10. IMPORTANT RESULTS!!!! • New atomic model • Atom mostly empty space • Tiny, dense central core – nucleus

  11. Rutherford's gold foil experiment

  12. Contains all the atoms positive charge • Volume of space in which the electrons move huge compared to volume of the nucleus

  13. Book analogy: • If an atom had a diameter of 2 football fields, the nucleus would be the size of a nickel!

  14. Don’t you wish you were here right now?

  15. WELL YOU’RE NOT – SO PAY ATTENTION!!!!!!!!!!!!!!!!!!!!!

  16. Atomic Theory song!!!

  17. NUCLEONS – particles located within the nucleus • Protons and neutrons • Protons • Positive charge • Mass of 1 amu (atomic mass unit)

  18. Neutrons • No charge (neutral) • Mass = 1 amu

  19. Electrons • Located outside the nucleus in “shells” • Each carries one unit of negative charge • Mass 1/1840 amu • Pg. 106 chart for subatomic particles

  20. Atomic number • Number of protons in the nucleus • Identifies the atom as an atom of a particular element • Determines its position on the Periodic Table • Atomic # = #protons = #electrons

  21. MASS NUMBER • Number of protons + number of neutrons • Number of neutrons = mass number – atomic number Isotopes

  22. Isotope Notation • Pg. 112 Sample and practice

  23. Average atomic mass • Weighted average of the naturally occurring isotopes of that element • Is a decimal because of the existence of isotopes • Pg. 114 Table 4.3 • Pg. 116-117 #21-24 • Video: How to Calculate an Average Atomic Weight.

  24. Periodic Table • Arrangement of elements where the elements are separated into groups bases on a set of repeating properties • Can compare properties of elements based on their position on the table

  25. Arranged according to increasing atomic number • Horizontal rows – periods • Vertical columns – groups (families) • Elements within a group have similar chemical and physical properties

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