1. Periodic Trends: Electronegativity, Metallic Character

2. Electronegativity
An atom’s ability to pull electrons to itself in a chemical bond
Cannot be directly measured
Trend: increases
decreases

3. How does this affect atoms?
Chemical bonding
Ionic Bonds
Formed between 2 atoms with a HUGE difference in electronegativity---electron cloud is pulled closer to the more electronegative atom.
Covalent Bonds
Atoms equally sharing electrons (nonpolar covalent)
Atoms with a difference in electronegativity will exhibit unequal sharing with the more electronegative atom pulling electrons toward it (polar covalent)

4. Example 1: Which of the following atoms is the most electronegative? SAs P Se Cl Br

5. Example 2:
Which of these atoms are arranged based on DECREASING electronegativity?
C > Si > P >As > Se
O > P > Al > Mg > K
Na > Li > B > N > F
K > Mg > Be > O > N
Li > Be > B > C > N

6. Metals, Nonmetals, Metalloids
How can you identify a metal?
What are its properties?
What about the less common nonmetals?
What are their properties?
And what the heck is a metalloid?

7. A Different Type of Grouping
Besides the 4 blocks of the table, there is another way of classifying element:
Metals
Nonmetals
Metalloids or Semi-metals.
The following slide shows where each group is found.

8. Metals
Metals are shiny, malleable, ductile, and are good conductors of heat and electricity.
They are mostly solids at room temp.
Want to LOSE valence electrons
Form positive ions
s block (not H and He), d/f blocks, some p block elements

9. Nonmetals Nonmetals are the opposite. No color, no shine
They are dull, brittle, nonconductors (insulators).
Gases at room temperature
Want to GAIN electrons
Form negative ions
p block elements, H and He

10. Transition Metals Middle of the periodic table
Forms positive ions, multiple types
Shine, malleable, ductile, good conductors
s/d orbitals—electrons lost from these subshells.

11. Metalloids/Semi-Metals
Metalloids, aka semi-metals are just that.
They have characteristics of both metals and nonmetals.
They are shiny (like metals) but brittle.
And they are semiconductors.
“on the fence, middle of the road”
B, Si, As, Te, At, Ge, Sb, Po

12. Noble Gases Group 18 (He, Ne, Ar, Kr, Xe, Rn)
Do NOT react with other elements
Atmospheric gases
Naturally in elemental form , single atoms
Not completely unreactive

13. Metallic Character
This is simply a relative measure of how easily atoms lose or give up electrons.
Tendency to LOSE electrons
Related to atomic radius/ionization energy, how easy to remove electrons

14. Metallic Character
Decreases
Increases

15. Nonmetallic Character
Atoms with a tendency to GAIN electrons
Increases
Decreases

16. Homework
Beer’s Law Lab Report
Read over your lab procedure