1. Chapter 6A: Chemical Bonding
General Chemistry
Mr. Mata
Cartoon courtesy of NearingZero.net

2. Standard 2a
Atoms combine to form molecules by sharing electrons to form covalent or metallic bonds.

3. Essential Question
How do electrons behave during bonding?

4. 6-1 Chemical Bonds Forces that hold atoms together.
make groups of atoms function as a unit.
Ionic bonds – transfer of electrons. Metal + Nonmetal Ex: NaCl, Li2O
Covalent bonds – sharing of electrons. Nonmetal + nonmetal Ex: H2O, CO2
Metallic bonds- electrons are free to move throughout material. Ex: Metals

5. Covalent Bonds Nonpolar-Covalent bonds (H2)
Electrons are equally shared.
Electronegativity (EN) values are used.
H: EN value = 2.1; H-H; 2.1 – 2.1 = 0
EN difference (0 to 0.3).
Polar-Covalent bonds (HCl)
Electrons are unequally shared.
H: EN value = 2.1; Cl: EN value = 3.0
3.0 – 2.1 = 0.9
EN difference (0.3 to 1.7)

6. Using Electronegativity differences
NaCl /0.9 – 3.0/= 2.1
Cl = (look on Periodic Table)
Na = or up = Ionic Bond

7. 6-2 Covalent Bonding
Molecule- smallest unit of matter that can exist & retain all properties of substance.
Examples: H2O & O2, C12H22O11
Diatomic molecule- molecule containing 2 identical atoms. (H2 N2 O2 F2 Cl2 Br2 I2)

8. Comparing Monatomic, Diatomic, and Polyatomic Molecules

9. Characteristics of the Covalent Bond
When two atoms form a covalent bond, their shared electrons form overlapping orbitals.
Bonding of two H atoms allows each atom to have stable e - configuration of helium, 1s2.

10. Chemical Formula- represents relative # of atoms in a chemical compound by using symbols & subscripts.
Example: H2O H=2 atoms O=1 atom
Molecular compound (Covalent) - simplest formula unit are molecules.
Have low melting & boiling pts.
Molecular formula- shows types & #’s of atoms combined in a single molecule.

11. Bond Length- average distance between 2 bonded atoms.
Bond Energy- energy required to break a bond.
Gives info about strength of bond.
Energy is stored in chemical bonds.

12. The Octet Rule
Compounds form so that each atom has an octet (8) e-’s outer shell.
By gaining, losing, or sharing e-’s.
8 is Great! H He

13. Electron-Dot Diagrams
Keeps track of valence (outermost) e-’s.
Valence e-’s of an atom shown by dots placed around the element’s symbol.
Inner-shell e-’s are not shown.

14. Lewis Dot
Shows how valence e-’s are arranged among atoms in a molecule.
Stability of compound relates to noble gas e- configuration.
CH4
H2O

15. Structural Formula
Shows shared pair of e-’s by a dashed line.

16. Single bond- 1 pair of e-’s
Double bond- 2 pair of e-’s
Triple bond- 3 pair of e-’s
Try a couple:
O O = O
N2 N N

17. Molecular/Covalent Compounds
Write Lewis Structures for Molecular Compounds. Electrons are shared: H2 . . H + H
H:H : : : : . :
:Cl:Cl:
Cl2
Cl. + Cl : : : : :

18. Lewis Structures
Often bonding pairs of electrons can be represented with a line:
HCl
H2O : : . : . H
Cl:
H:Cl: + =
H-Cl: : : : : : : : H : .
H:O: = O:
H-O: . : H H . . . H

19. Lewis Structures NH3 H . . 3H . H-N: + N: . H H . 4H . CH4 + . . C