3.  There are general trends in the properties of atoms and their ions with increasing atomic number.  These trends can be explained using the periodic table.

4.  Can you name a trend that we have talked about this year?  Think about what you graphed  Atomic Mass vs Atomic # As Atomic # increases, Atomic Mass increases  Atomic Radius vs Atomic # As Atomic # increases, Atomic Radius increases down a group, but decreases across a period.

5. Atomic Radius vs Atomic Number Atomic Radius (pm) Atomic Number (protons) Period Trend As you proceed from left to right across a row (period), the atomic radius decreases (the atoms get smaller). Why????

6. Period The period # indicates how many energy levels the atoms in that period have. Notice the increasing number of protons…. SO….as the number of protons increases, the outer electrons are pulled in closer to the nucleus and the atomic radius gets smaller!

7. Atomic Radius vs Atomic Number Atomic Radius (pm) Atomic Number (protons) Group Trend As you proceed down a group (family or column), the atomic radius increases (the atoms get larger). Why???

8. The period # indicates how many energy levels the atoms in that period have. H Li Na K So…As you proceed down a group, the number of energy levels increases. This increases the atomic radii of the atoms. Row 1 Row 2 Row 3 Row 4

9. http://www.youtube.com/watch?v=xjEJl88AYMo http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/atomic4.swf

10.  Which atom is larger, Al or Si? Why????  Which atom is smaller, Br or I? Why????

12.  Electrons can move between energy levels (Bohr ’ s model supported by line spectra)  The nucleus and electrons are attracted to each other (opposites attract)  Electrons that are far away from the nucleus can escape the attraction of the nucleus (atoms can lose electrons)  Losing an electron is called ionization

13.  Ionization energy is the energy required to remove a valence electron from an atom.  Valence electron= outermost electron that is farthest from the nucleus. group period

15. D I

16. D  Energy needed to remove a loosely held electron from an atom  Decreases as you move down a group Atom gets bigger, more energy levels Nucleus is further from the outer most electron (valence electrons) Nucleus & electron attraction decreases, so it is easier to take an electron away.

17. I D  Energy needed to remove a loosely held electron from an atom  Increases as you move across a period Nonmetals hold onto their electrons tighter Atom is smaller, so nucleus is closer to valence electron making it harder to remove.  http://www.youtube.c om/watch?v=o6tv03D R_Gg http://www.youtube.c om/watch?v=o6tv03D R_Gg

18. Which has higher ionization energy? He or Xe? (kJ/mol) He Xe 2372 kJ/mol 1170 kJ/mol Smaller atom, He holds on tighter to valence electron Practice

19.  Metals have a low Ionization Energy want to lose e -s to become stable  NonMetals have a high Ionization Energy do not want to lose e -s, want to gain e -s

20. Which has higher ionization energy? Li or Ne? (kJ/mol) Li Ne 520 kJ/mol 2081 kJ/mol Ne holds onto atoms tighter Practice