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Outline the history of the atomic model.

Outline the history of the atomic model. Agenda for Tuesday Dec 14 th Atoms Atomic mass, #, protons, etc. Atoms. Nucleus in the center Protons and neutrons Electrons on outside of nucleus Electron cloud model Electrons exist in energy levels – based on # of electrons.

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Outline the history of the atomic model.

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  1. Outline the history of the atomic model. Agenda for Tuesday Dec 14th • Atoms • Atomic mass, #, protons, etc

  2. Atoms • Nucleus in the center • Protons and neutrons • Electrons on outside of nucleus • Electron cloud model • Electrons exist in energy levels – based on # of electrons

  3. Atomic Number and Atomic Mass Element name boron 5 Atomic number B Symbol 10.811 Atomic mass

  4. Atomic number: # of protons in nucleus • Each element has a different atomic # • Identifies the element • Hydrogen = smallest atomic # (1) • # of protons = # of electrons

  5. Atomic mass: total mass of protons and neutrons in an atom, measured in atomic mass units (amu) • Atomic weight • Atoms of the same element can have different numbers of neutrons - isotopes • # on periodic table is the average atomic mass for that element

  6. We will round the average atomic mass to get a whole # called the mass number. • Examples: Sodium (Na) Avg. atomic mass = 22.990 amu Mass # = 23 Nitrogen (N) Avg. atomic mass = 14.007 amu Mass # = 14

  7. Finding # of neutrons mass # - atomic # = # of neutrons For Na: 23 – 11 = 12 neutrons For N: 14 – 7 = 7 neutrons

  8. Practice

  9. Find the mass number, protons, neutrons, and electrons for Bromine. Agenda for Wednesday Dec 15th • History of the Atom Flash Cards • Practice with mass, protons, etc • Isotopes

  10. 6 6 6 Oxygen 8 16 1 1 0 Carbon 6 8 1 1 3 7 7 7

  11. Isotopes • Atoms of the same element can have different numbers of neutrons  isotopes • # of protons and electrons stays the same for a particular element • Mass changes • Means # of neutrons changes • Atomic mass on your P.T. is an average of all the isotopes • For Boron: .8 (10 amu) + .2 (11 amu) = 10.811 amu

  12. More on Isotopes • Because the numbers of neutrons in the isotopes are different, the mass numbers are also different • You use the name of the element followed by the mass number of the isotope to identify each isotope: boron-10 and boron-11

  13. Example: • Neon. All neon atoms have 10 protons and 10 electrons. Some neon atoms have 10 neutrons and some have 12. • Both isotopes of neon

  14. Mass # (protons + neutrons). Different for each isotope Ne or Ne-20 Ne or Ne-22 20 10 Atomic # (# of protons) Mass # (protons + neutrons). Different for each isotope 22 10 Atomic # (# of protons)

  15. What’s the point of Isotopes • You can tell how old something is • Radiocarbon Dating • Use as markers in research • Follow a certain molecule, atom

  16. Practice ProblemsYou will need your periodic table! • For Mg-25: How many protons, electrons, and neutrons? • For N-15: How many protons, electrons, neutrons? • For P-31: How many protons, electrons, neutrons?

  17. Practice

  18. What is an isotope? Agenda for Thursday Dec 16th • Mass #, Atomic weight, proton review • Valence Electrons • Lewis Dot Structures

  19. Atoms • Nucleus in the center • Protons and neutrons • Electrons on outside of nucleus • Electron cloud model • Electrons exist in energy levels – based on # of electrons

  20. Valence Electrons • Electrons in the outermost energy level • Valence electrons determine reactivity and other chemical properties • 8 valence electrons means a stable atom = do not want to react with other atoms

  21. Where are electrons found? Nucleus Least likely Most likely

  22. Valence electrons Help! We’re so vulnerable! • A way to draw an atom showing where electrons are found 13 p+ 14 n0

  23. Valence electrons Carbon -12 has 4 electrons in the last energy level . . . therefore carbon-12 has 4 valence electrons

  24. 2nd shell can hold 8 e- 1st shell can hold 2 e- Nucleus 3rd shell can hold 8 e- Bohr’s Model

  25. How many electrons in each shell? • 1st shell = 2 electrons • 2nd shell = 8 electrons • 3rd shell = 8 electrons • 4th shell = 18 electrons

  26. Drawing Carbon-12 with Bohr’s Model • Steps: • Find number of neutrons and protons. • 2. Find number of electrons. • 3. Fill in electrons, beginning with the 1st energy level.

  27. How many valence electrons does Nitrogen have? NUCLEUS

  28. How many valence electrons does Calcium have? Calcium has 2 Valence electrons NUCLEUS

  29. How many valence electrons does Phosphorous have? Phosphorous has 5 Valence electrons NUCLEUS

  30. How many valence electrons does Boron have? Boron has 3 Valence electrons NUCLEUS

  31. Cool Trick! 1 8 3 5 4 2 7 6

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