A quick overview of chemical bonding!

1. Chemical Bonding: Ionic,
Covalent, and Metallic
By: Sakina Haji
Pd. 6

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 types: Ionic, Covalent, and Metallic

3. Ionic Bonds
 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

4. 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.

5. Covalent Bonds
 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).

6. 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.

7. 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.

8. Covalent vs. Ionic

9. Metallic Bonds
 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.

10. 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.

11. 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.

12. 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