The document discusses chemical bonding, which occurs when atoms bond together to form more stable arrangements with lower energy than as isolated atoms. Atoms bond by gaining, losing, or sharing valence electrons to achieve stable electron configurations like noble gases, following the octet rule where atoms gain or share electrons to have 8 in their outer shell. The main types of bonds are ionic involving electron transfer, covalent involving electron sharing between nonmetals, and metallic involving delocalized electrons in metals.

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