This document discusses the three main types of chemical bonds: ionic, covalent, and metallic. Ionic bonds form between ions when electrons are transferred from metals to nonmetals. Covalent bonds form when atoms share electrons in either single, double or triple bonds. Metallic bonds occur when metal atoms contribute electrons to form a "sea of electrons" that are free to move between atoms. Each bond type has distinct properties related to bonding strength, lattice structure, conductivity and melting/boiling points.

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.