1. Chemical Bonding

3. Review: valence electrons
Valence electrons are the electrons found in the outermost energy level of the atom
Valence electrons are responsible for forming chemical bonds
TO THE RIGHT: Atoms of nitrogen have 5 valence electrons

4. Review - Octets
When an atom has eight valence electrons it has an octet
Octets are chemically stable
Atoms want to be stable, so they will gain, lose or share electrons to have an octet (BONDING)

5. Why do atoms bond?
We learned that octets (a full valence electron shell) are very stable. Atoms desire stability, so they will combine with other elements in order to achieve a full octet of valence electrons.
To become more stable by filling their outer energy level with electrons (8)

6. Valence Electrons and the Periodic Table
The periodic table is divided into groups which are columns of elements with similar properties
Elements in the same group will have the same number of valence electrons (exception: transition metals)

7. Three Main Types of Bonding
Ionic bonding –a metal and a nonmetal
Covalent bonding – a nonmetal and a nonmetal
Metallic bonding –a metal and a metal

8. What type of bond is it? a) Ca & S b) Li & Pt c) C & Cl
Find the following elements on the periodic table and determine their bond type:
a) Ca & S
b) Li & Pt
c) C & Cl

9. Ionic Bonding
Metal and non-metal (one is way more electronegative than the other)
Metal loses e- and becomes positive (“cation”)
Nonmetal gains e- and becomes negative (“anion”)
Opposites attract: the ions bond via opposite charges

11. PROPERTIES OF IONIC COMPOUNDS
Crystalline solids – usually hard crystals
High melting and boiling points –
because of strong forces in the bond
Soluble in water –
water molecules attract the ions
Conduct electricity (electrolyte)

13. Covalent Bonding
Two or more nonmetals (not a large electronegativity difference)
SHARE electrons (the outer energy levels overlap)
1, 2, or 3 electrons shared (single, double, or triple bond)

15. COVALENT COMPOUNDS: Soft and brittle
Low melting and boiling points – because covalent bonds are weak
Insoluble in water –
except if dipole moment
Do NOT conduct electricity -
non-electrolyte

16. Metallic Bonding Metal and a metal
Metals are held together in rigid shapes
The nuclei are attracted to delocalized electrons from other atoms

17. Review Questions: Why do atoms bond?
Which type of bond shares electrons?
What is a cation? Does the metal or the nonmetal become the cation?
What is a triple bond?
What types of compounds are soft? Do they conduct electricity?
What is an electrolyte?