1. Periodic means cycle or repeating pattern.
Periodic Trends
Patterns in the physical and chemical properties of the elements are called trends.
Periodic means cycle or repeating pattern.

2. Periodic Trends in Atomic radius
Group trends- Radius increases as electrons (must fill new energy levels) and are added to atom.
Atomic mass, and number increase in this direction also. r

3. What happened to energy levels as p+ and e- increased across a row?
How does this affect atomic radius across a row?

4. Periodic Trends in Atomic radius
Period trends- Radius decreases as electrons fill across same energy level. Filled inner levels shield outermost electrons from the nucleus
(So in any period, between the nucleus and outer electrons, there is the same number of electrons.)
This trend is opposite for atomic mass & number.

6. Electronegativity Metal vs. Nonmetal
Where are the metals vs. the nonmetals?
Nonmetals have high electronegativity.
Metals have low electronegativity

7. Electronegativity vs. atomic size
Where are the smallest atoms in a period?
Big atoms have lower electronegativity

8. Electronegativity explained
Valence electrons of small atoms that are closer to the nucleus than larger atoms, tend to be held to the nucleus with stronger forces of attraction. Usually the farther they are away, the weaker the forces of attraction. e- e-
High or strong attraction to valence electrons in a bond = High Electronegativity.

9. First Ionization Energy
This is the amount of energy it takes to remove the first or outer most electron.
Look on your periodic table at first ionization potential in V, or on page in textbook.
How easy is it to remove electron from the Group I & II metals? From the halogens?

10. First Ionization Energy

11. How might the first ionization energy compare to the electronegativity across the first period?

12. They are very similar!

13. Trends Important to Bonding
Ionization energy was used to help determine electronegativity.
Electronegativity is a scale in the units of Paulings, developed or calculated to show the degree one element tends to have the bonding electron(s) in a pair of oppositely charged ions.
NaCl e- e-

14. For example + Cl
3.12 K
0.82 -
The electronegativity of nonmetal Cl- is 3.12
And the electronegativity of metal K+ is .82
The difference between the two is 2.30 Pauling units
We determine the percent ionic character of the bond to be 74%. By definition this is considered ionic bonding since it is more than a 2.0 difference.

15. To determine bond type: Calculate the difference in Electronegativity between these Element Pairs
Difference > 2.0 = ionic
Difference < 2.0 = covalent
0.35
3.0
C and H
Li and F
0.94
Na and F
3.05
N and H
K and F
3.16
0.48
S and H
(Formula Units of bonded ions)
1.43
C and F
(Molecules of bonded atoms)

16. Write electron configurations of the following:
1. Ca Br-1
2. Al S-2
3. K N
4. Kr [Ar] 4s2 3d10 4p6
5. Ar 1s2 2s2 2p6 3s2 3p6
6. 1s2 2s2 2p3
1. Ar 1s2 2s2 2p6 3s2 3p6
2. Ne 1s2 2s2 2p6
3. 1s2 2s2 2p6 3s2 3p64s1

17. Use electron dot diagrams to determine chemical formulas of the ionic compounds formed when the following elements combine.
Example:
K and I
Ca and S +1 -1 -2 +2 K I Ca S