This goes over bonding and how electrons fill their outer shell to become more stable.

1. Warm Up:
1. What is the total number of electrons in all
the s-orbitals of a neutral atom of
phosphorus?
2. The electron configuration of a neutral
calcium atom is shown below.
1s2
2s2
2p6
3s2
3p6
4s2
How many valence electrons are in the
atom?

2. Introduction to Chemical Bonding
• Most atoms do not exist freely as isolated
atoms in nature (except for noble gases).
• Most atoms tend to bond to other atoms to
form more stable arrangements.
– lower energy state than as free atoms
– filled outer energy level

3. Chemical Bond – a link (glue) that holds
two atoms together.
• What part of an atom is involved in chemical bonding?
 Electrons in the highest energy level.
 These electrons are called valence electrons.
• The periodic table can be used to determine the number
of valence electrons an atom has.
 s-block - number of valence electrons equal to group
number.
 p-block - number of valence electrons equal to group
number minus 10
 d-block - usually 2 valence electrons - Why?

4. Electron Dot Notation
• Electron-dot notation is used to represent an atom’s
valence electrons.
– Write the symbol of the atom.
– Use dots to represent valence electrons. Put one
dot on each side of symbol before doubling
(RLTB).
– Example: Sulfur (S)
• The maximum number of valence electrons an atom
can have is eight.

6. Octet Rule
• Noble gas atoms are unreactive because their
electron configurations are especially stable.
– This stability results from the fact that the noble-
gas atoms’ outer s and p orbitals are completely
filled by a total of eight electrons. (except He)
• OCTET rule: chemical compounds tend to form so
that each atom, by gaining, losing, or sharing
electrons, has eight electrons in its highest energy
level (except H).

7. Types of Chemical Bonds
• The two of the most common types include:
a) Ionic bonding – involves the transfer of valence
electrons from one atom to another (metal +
nonmetal)
b) Covalent bonding – involves sharing of valence
electrons between two atoms (nonmetal +
nonmetal)
c) Metallic bonding – involves metals bonding and
forming a “sea of electrons”

8. Bonding Types

9. • Can use the difference in electronegativities
between two atoms to predict the type of
bond formed between the atoms.
• Table of values on page 161 in book
Bond Type Electronegativity
Difference
Nonpolar Covalent 0 – 0.2
Polar Covalent 0.3 – 1.7
Ionic 1.8 or greater

10. Here’s the page, with values.

11. What Do You Think
• Use electronegativities to determine the type
of bond that will form. If the bond is polar,
decide which atom is partially negative and
which is slightly positive.
(a) C and S
(b) Na and O
(c) P and Cl