1. Periodicity Announcement: Test next Thursday (B)/Friday (G)
Have your homework out. Coming around to check!

2. Electron configuration
Period number that element resides on the table is equal to number of energy levels
S, p, d, f blocks

3. Valence electrons
Elements in each column of the periodic table have same number of valence electrons
The number of valence electrons change from as you move from left to right across periodic table (except transition metals)

5. Valence Electrons and Reactivity
Elements with same number of valence electrons tend to react in similar ways
Elements tend to react in ways that allow them to achieve configuration of nearest noble gas
Stable octet: full electron shell, most stable configuration

6. Classes of Elements
Metals – elements that have luster, conduct heat and electricity (e.g. copper jewelry, polished silverware)
Nonmetals – most are gas at room temp, do not conduct electricity, poor conductor of heat than metals (e.g. oil – carbon rich)
Metalloids – semiconductor (does not conduct electricity as well as metal but conducts better than nonmetal) (e.g. silicon in microchips of electronics)

7. Alkali Metals (Group 1) Alkaline Earth Metals (Group 2)
Metals that react vigorously with water
Must lose one valence electron to achieve stable octet
Always found as compounds
Alkaline earth metals
Slightly less reactive than alkali metals
Must lose two valence electrons to achieve stable octet
Usually found as compounds

8. Transition Metals (Groups 3 – 12)
Less reactive than alkali metals and alkaline earth metals
Must lose 1, 2 or 3 valence electrons to achieve stable octet
Some metals are so unreactive that they seldom form compounds with other elements

9. Halogens (Group 17) Noble Gases (group 18)
Most reactive group of non metals
Gain one electron needed to have stable octet
Noble gases
Low reactivity
Stable octet achieved

10. Atomic Radius Size of atom
Measured by distance from center of an atom’s nucleus to its outermost electron in the electron cloud

11. Ionization energy
Ionization energy: amount of energy needed to remove one (outermost electron from an atom)
Energy required to remove one electron = first ionization energy

12. electronegativity
Measure of the ability of an atom in a chemical compound to attract electrons
The atom with higher electronegativity will pull on the electrons more strongly that other atoms will

13. Atomic radius – down the group
Addition of another level of electrons increases size of atom
Valence electrons found in energy levels farther and farther from the nucleus

14. Atomic radius – across the period
Increase in protons (nuclear charge) across the period ‘pulls’ outer electrons more strongly towards nucleus
 small size

15. Ionization energy – Down group
Electron shielding = decrease in attraction of electron and nucleus
More electrons than protons as you move down the group  decrease in ionization energy

16. Ionization energy – across a period
Number of protons and number of electrons increase by one each  increase in ionization energy

18. Electronegativity trend
Decrease down group due to electron shielding (decrease in attraction of electron and nucleus)
Increase across a period – electrons attracted much more strongly