2. WHAT IS A CHEMICAL BOND?
‡ A chemical bond holds two atoms together.
‡ It is formed by the attraction of a positive and a
negative ion or by the attraction of a positive
nucleus to negative electrons.
‡ Atoms form chemical bonds to get eight valence
electrons, to complete the octet rule and to
become stable.

3. THERE ARE 3 TYPES OF
CHEMICAL BONDS
• Ionic
• Covalent
• Metallic

4. • Ionic bonds form between cations (metals)
and anions (nonmetals).
• The metal transfers its valence electron to
the nonmetal. The nonmetal accepts the
valence electrons and turns into a negative
ion, while the metal becomes a positive ion.
• Arranged in a pattern of a crystal lattice
• High melting and boiling points
• Hard, rigid, and brittle

5. IONIC BONDS: ENERGY
• The formation of ionic compounds is exothermic.
• The energy required to separate ions is called the lattice energy.
The more negative the lattice energy, the stronger the force of
attraction.
• Lattice energy of smaller compounds is more negative than that of
larger compounds because the nucleus holds the valence electrons
more closely together.

6. • Instead of transferring electrons, atoms share electrons.
• If one pair of electrons are shared, a single bond is formed
(Group 17 elements form single bonds).
• If multiple pairs of electrons are shared, double and triple
bonds can be formed (carbon, nitrogen, oxygen, and
sulfur usually form multiple bonds).

7. COVALENT BONDS: SIGMA VS. PI
• Single covalent bonds are called sigma bonds. Occurs
when the electron pair is shared in an area centered
between the two atoms. A sigma bond results if the
valence atomic orbitals overlap end to end.
• A pi bond is formed when parallel orbitals overlap to
share electrons. The shared electron pair occupies the
space above and below the place where the atoms are
joined.
• A double bond has one sigma and one pi bond. A
triple bond has one sigma bond and two pi bonds.

8. COVALENT BONDS: ENERGY
• Bond length: Distance between the atoms
• Bond dissociation energy: Amount of energy required to bread a
covalent bond
• The smaller the bond length, the greater the bond dissociation
energy, and vice versa.

9. COVALENT VS. IONIC

10. • When metals bond together to
complete the octet rule.
• All metal atoms contribute their
valence electrons to form a sea of
electrons. Electrons are free to
move b/w the atoms.

11. METALLIC BONDING: ALLOYS
• An alloy is a mixture of elements that has metallic properties.
• Properties of alloys are different from those of the elements in it.
• Alloys most commonly forms when elements involved are similar
in size or the atoms of one element are considerably smaller than
the atoms of the other.
• There are two types of alloys, substitutional and interstitial.

12. METALLIC BONDS: ENERGY
• Metallic bonds are weak and little
energy is needed to break the bonds.
Therefore, they have high melting
points
• Because the electrons are mobile,
they transfer heat more efficiently
and, therefore, are better
conductors.

13. CONCLUSION
• Elements bond to become stable.
• Elements bond to have 8 valence electrons.
• 3 types of bonds: Ionic, Covalent, Metallic
• In ionic bonds, one element gives its electrons to another element.
• Covalent bonds are the strongest bonds. Elements share electrons.
• Metallic bonds are the weakest bonds. Elements are in a sea of
electrons