1. COVALENT BONDING

2. COVALENT BONDS Covalent bonds = Sharing electrons
Octet rule: Atoms still need to become stable by having 8 electrons in their outer energy level!!
Instead of losing or gaining valence electrons, atoms in covalent bonds share valence electrons
These bonds take place between nonmetals and nonmetals

3. COVALENT BONDS
Atoms that combine through covalent bonds (electron sharing) form molecules
Example:
Nonmetal

4. COVALENT BONDS Compound Properties
Have lower melting and boiling points than ionic compounds
- No bonds to be broken as in ionic compounds
- Molecules are very close to each other, but not bonded
Are soft and “squishy,” compared to ionic compounds
- Molecules move very easily around each other because there are no bonds between them
- These makes them flexible and not hard

5. COVALENT BONDS Compound Properties
They are more flammable than ionic compounds
- Most covalent compounds have carbon and hydrogen which burn very easily with oxygen
- Those without carbon and hydrogen do not burn
They do not conduct electricity in water
- Ion (charge carriers) movement in water is the conduction of electricity
- Covalent compounds do not have ions
They are usually not very soluble in water
- “Like dissolves like” rule
- Compounds dissolve in compounds with similar properties
- Water is polar solvent and most covalent compounds are nonpolar = then do not dissolve in water

6. Single covalent bonds Made up of two shared electrons
Usually, one of the shared electrons comes from one of the atoms in the bond and the other electron from the other atom in the bond
Halogen (Group 7A) elements exist as molecules of single covalent bonds (more stable)
Example: Hydrogen molecule (H ) 2

7. Single covalent bonds Hydrogen Molecule. . . . H H H H +
Each hydrogen atom has 1 valence electron
Bonding pair
Another way to represent the hydrogen covalent bond: H H
Bonding pair

8. Single covalent bonds Water Molecule. . . . . . . . . . . . . H H . O + + H O . . H OR . . . . H O H

9. Multiple Covalent Bonds
Covalent bonds can have more than one pair of shared electrons
Atoms of the elements carbon, nitrogen, oxygen, and sulfur very often form multiple covalent bonds
Multiple bonds can be double or triple covalent bonds

10. Double covalent bonds Oxygen Molecule. . . . . . . . . . . . . . . . O . O . . O . + O
Each oxygen atom has 6 valence electrons
Bonding pairs

11. Triple covalent bonds Nitrogen Molecule. . . . . . . . . . . . N . N . N N +
Each nitrogen atom has 5 valence electrons
Bonding pairs

12. How do elements combine?

13. Naming Covalent Compounds
Names are usually composed of two words
- First is the name of the first element in the formula
- Second is the name of the second element in the formula, but changing the ending to –Ide
Example: HF = hydrogen fluoride

14. Naming Covalent Compounds
If there is more than one atom of an element in the molecule, then we need to use prefixes to tell us how many are there
Number of Atoms
Prefix 1
Mono- (use only for oxygen) 2
di- 3
tri- 4
tetra- 5
penta- 6
hexa- 7
hepta- 8
octa- 9
nona- 10
deca-

15. Naming Covalent Compounds
Some common names to some very important covalent compounds
Formula
Common Name
Molecular Compound Name
H O
water
dihydrogen monoxide NH
ammonia
nitrogen trihydride
N O
nitrous oxide (laughing gas)
dinitrogen monoxide NO
nitric oxide
nitrogen monoxide CH
methane
carbon tetrahydride 2 3 2 4

16. Naming Covalent Compounds
Examples……
P O = diphosphorus pentaoxide
CO = carbon monoxide
CF = carbon tetrafluoride 2 5 4