1. Chemical Bonding

2. Chemical Bond
The forces that hold groups of atoms together and make them function as a unit
Bonding involves only the valence electrons
There are 2 types of bonds:
Ionic: Transfer of electrons from a metal and to a nonmetal
Covalent: Sharing of electrons between 2 nonmetals
Note: When 2 metals bond an alloy is formed
Electrons are transferred or shared to give each atom a noble gas configuration (stable octet)
This is known as the octet rule

3. Lewis Diagrams
Valence electrons involved in bonding can be represented by Lewis dot diagrams
A chemical symbol represents the nucleus and the core electrons (not involved in bonding).
Dots around the symbol represent valence electrons.

4. Drawing Lewis DiagramsCl
Write the element symbol.
Draw dots, one for each valence electron
Dots should be spread over 4 sides
It does not matter what side the dots are placed, but do not start to pair dots until there is one on each side
The number of valence electrons is equal to the group number. With one exception.

5. Lewis diagrams for the first 20 elements

6. Ionic Bonding

7. Ionic Bonding Involves the transfer of valence electrons
Attraction between a cation and an anion
Cation
Positively charged ion
Typically metals
But could be a polyatomic ion
Anion
Negatively charged ion
Typically nonmetals
But could be a polyatomic ion

8. Ionic Bonding

9. Ionic Bonding
The oppositely charged ions are attracted to each other by a force called an ionic bond

10. Properties of Ionic Compound
Most ionic compounds:
Have high melting points
Are hard and brittle
Are soluble in water
Form electrolytes (conduct electricity) when dissolved in water

11. Crystal Lattice Structure
Ionic compounds form crystal lattices
This explains why they have high melting points and are hard but brittle
Na+
Cl-

12. Ionic Compounds in Water
When ionic compounds dissolve, they separate into their ions
The free ions can now move and conduct electricity

13. Representing Ionic Compounds Lewis Diagrams
Formation of sodium chloride: Cl
· ·
Na+ [ ] Cl
· · Na +

14. Lewis Structures for Ionic CompoundsBa • O •• •• O Ba 2+ 2-
Ba and O
BaO Mg • Cl •• •• Cl Mg 2+ - 2
Mg and Cl
Binary ionic compounds.
Note the types of arrows used to move electrons – fishhooks for single e-.
Write the Lewis symbol for each atom Determine how many e- each atom must gain or lose.
Use multiples of one or both ions to balance the number of electrons.
MgCl2

15. Representing Ionic Compounds Criss-Cross Method
For monatomic ions:
Take the absolute value of the ionic charge for the cation and make it the subscript for the anion and vice versa.
Example: Al3+ and Cl-
The 3 becomes the subscript for the chloride ion and the 1 becomes understood for aluminum.
Forming aluminum chloride: AlCl3

16. Representing Ionic Compounds Criss-Cross Method
For polyatomic ions:
Additional step of including brackets around the polyatomic ion if it has a subscript other than one.
Example: Mg2+ and OH-
The 2 becomes the subscript for the hydroxide ion, but brackets are needed to indicate 2 of each the O and the H.
The 1 becomes the understood subscript for Mg.
Forming magnesium hydroxide: Mg(OH)2

17. Polyatomic Ions NICK the CAMEL ate a CLAM for SUPPER in PHOENIX
Underlined letter represents the symbol of the element.
The consonants represent the number of oxygen
The vowels represent the negative charge.
Eg. Underlined letter= N
Number of consanants= 3 represents oxygens
Number of vowels= 1 represents charge
NO3- Nitrate

18. Covalent Bonding

19. Covalent Bonding Electrons are shared between two nonmetals
Weaker attractive force than ionic bonding

20. Properties of Molecular Compounds
State at SATP
Typically gases & liquids, but some solids
Structure
Variable (waxy to brittle)
Melting & Boiling Points
Low
Electrical Conductivity
Nonelectrolyte
Solubility in Water
Variable (low to high)
Confused?? Don’t worry…more answers to come

21. Covalent Bonding Formation of hydrogen chloride: Cl ® Cl H H +
Lone pairs, valence electrons not involved in covalent bond
Formation of hydrogen chloride:
· · Cl
· · Cl
· · H H +
® H - Cl
· ·
· ·
Covalent bond, shared electrons
Structural Formula: H-Cl (lone pairs are not drawn)

22. + Lewis Structures H H2: ® H H or H H Cl + ® Cl Cl Cl2: or Cl Cl+
H2:
® H H
or H H Cl
· · +
® Cl Cl
· ·
Cl2:
or Cl Cl
· ·
Structural Formula: Cl-Cl

23. Double and Triple Bonds
Atoms can share 4 electrons to form a double bond or 6 electrons to form a triple bond. =
O O
· ·
O2:
· ·
N N 
N2:
E.g. H, C, N, O, F
The number of shared electron pairs (covalent bonds) that an atom can form is the
bonding capacity.

24. Multiple Covalent Bonds• • N • •• •• N • • N •• • • N • •• N ••

25. Multiple Covalent Bonds• • • C O • ••
• • O • C • • • O
• •
• • •
• • • C O •• C O ••

26. Drawing Lewis Structures
Arrange the element symbols.
Central atoms are generally those with the highest bonding capacity.
Carbon atoms are always central atoms
Hydrogen atoms are always peripheral atoms
Add up the number of valence electrons from all atoms.
For polyatomic ions, add one electron for each negative charge and subtract one for each positive charge.
Draw a skeleton structure with atoms attached by single bonds.
Complete the octets of peripheral atoms.
Place extra electrons on the central atom.
If the central atom doesn’t have an octet, try forming multiple bonds by moving lone pairs.