1. Bonding

2. Bonding: electrical attraction between atoms’ nuclei and valence e-
Why bond?
More stability

3. Ionic vs. Covalent Bonding
Ionic bonds
Between metal and nonmetal only
e- are transferred
Joined by electrostatic forces
Very strong
Another name is salt
Most crystalline solids at room temp
Conduct electric current in molten state or in solution (electrolyte)
Movement of ions = flow of electricity

4. Covalent bonding Many molecules are gases and liquids
Have weaker bonds
e- are shared
Occurs b/t 2 nonmetals

5. Chapter 6 Ionic Compounds
Section 3 Ionic Bonding and Ionic Compounds
Chapter 6
Ionic Compounds
Most ionic compounds exist as crystalline solids. (minimize their potential energy)
A crystal of any ionic compound is a 3-D network of (+) and (-) ions mutually attracted to each other.

6. NaCl and CsCl Crystal Lattices
Section 3 Ionic Bonding and Ionic Compounds
Chapter 6
NaCl and CsCl Crystal Lattices

7. Electron-Dot Notation
Chapter 6
Electron-Dot Notation
To keep track of valence electrons, it is helpful to use electron-dot notation.
Electron-dot notation is an electron-configuration notation in which only the valence electrons of an atom of a particular element are shown, indicated by dots placed around the element’s symbol. The inner-shell electrons are not shown.

8. Drawing Lewis Structures
Count # valence e- of all atoms in compound; this is the number of e- you may work with
Most atoms like 8 e- surrounding them, except H (only 2 e-)
Space atoms out symmetrically with H’s on outside
Central atom is least EN atom, except if C is involved and NEVER H
Put 1 pair of e- in between each atom (shared pairs)
Put remaining e- around atoms (lone or unshared pairs)

9. Never make a multiple bond if you don’t have to Polyatomic Ions:
If there are not enough e- to put around as lone pairs, make a lone pair another shared pair (double and triple bonds)
Never make a multiple bond if you don’t have to
Polyatomic Ions:
Do same thing as before, but
Add # e- if it’s a negative charge
Subtract # e- if it’s a positive charge
Put ion in brackets with charge on outside

10. Resonance
Structure that occurs when it is possible to draw 2 or more valid e- dot structures
Double-headed arrows used to connect structures
EX: O3
SO2

11. Exceptions to Octet Rule
Cannot be satisfied in molecules whose total # is odd #
Some molecules have more or fewer than 8 e-
Atoms that have more than 8 e- usually bonded to highly EN atoms, like the halogens
bonding involves e- in d and f orbitals EX
BF3
SF6
PCl5

12. VSEPR [Valence Shell Electron Pair Repulsion]
Repulsion b/t e- prs causes molecular shapes to adjust so that valence-electron prs stay as far apart as possible
Determines geometry of molecules
See lab for shapes to know

13. Electronegativity and Polarity
Electronegativity (EN): how attractive an atom is to shared pair of e-; greater difference, more ionic and the more polar

14. Trends in EN on Per. Table
As you go across period left to right, atoms have same # E levels and same # shielding e-.
Increased nuclear charge = increased attraction of valence e- to nucleus
Therefore, EN increases
As you go down group, add more E levels and e-.
Increased shielding balances increased nuclear charge, which means less e- attraction to nucleus
Therefore, EN decreases
EXCEPTIONS: high values in d-block because d-orbitals shielded differently than s and p

15. Molecular Polarity Polar bonds often make molecules entirely polar
Molecules can be nonpolar but have polar bonds
When polar bonds cancel each other out
Ex: CO2

16. Metallic Bonding
The unique characteristics of metallic bonding gives metals their characteristic properties:
electrical conductivity
thermal conductivity
malleability
ductility
shiny appearance

17. In a metal, the vacant orbitals in the atoms’ outer energy levels overlap.
This overlapping of orbitals allows the outer electrons of the atoms to roam freely throughout the entire metal.
The electrons are delocalized, which means that they do not belong to any one atom but move freely about the metal’s network of empty atomic orbitals.
These mobile electrons form a sea of electrons around the metal atoms, which are packed together in a crystal lattice.

18. The chemical bonding that results from the attraction between metal atoms and the surrounding sea of electrons is called metallic bonding.