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The Chemical Bond
Ionic and Covalent Bonds
Chemistry
Ms. Piela
Ionic Compounds Overview
 Bonds formed between a metal and a
nonmetal
 Metals form positive ions called cations
 Trick to remember: “ca+ion”
 Non-metals form negative ions called
anions
 Ionic bonds are formed by a transfer of
electrons
Properties of Ionic Compounds
 Ionic compounds dissociate (or break apart) in liquids
 Example: Table salt in water
 Ionic compounds can conduct electricity
 If something conducts electricity, then ions/charges
must be able to move
 Solid ionic compounds are rigid, not allowing charges to
move
 Two conditions allow ionic compounds to conduct
electricity:
 Molten (or liquid)
 Dissolved in solution
 Example: Li-ion batteries
Properties of Ionic Compounds
Ionic compounds tend to
have high melting points
This is due to the high
strength of the ionic bonds
Stronger bonds need more
energy to break apart!
Formation of Ionic Compounds
 Ionic bonds follow the Octet Rule
 Octet rule – Each element tends to
form compounds based on the easiest
way to gain 8 valence electrons
 Example: Na and Cl
 Sometimes combinations are not an
easy one-to-one ratio!
 Example: Ca and Cl
Formation of Ionic Compounds
 Examples
 Mg and O
 K and S
 Practice
 Ba and N
 Li and P
Formation of Ionic Compounds
 Transition metal ionic compounds
 All form positive ions (cations), but
can form multiple ions
 Example: FeCl2 and FeCl3
Covalent Compounds Overview
 Covalent bonds are made between
nonmetals only
 Does NOT depend on charges!!
 Covalent bonds will share electrons
as both elements need to gain
electrons to obtain full outer shell
(8 valence electrons)
Properties of Covalent Compounds
 Forms longer bonds because bonds are
weaker than ionic bonds
 Energy is lowered when atoms form a
covalent bond
 This is the main driving force behind
their formation
 There is a balance between their
attractive and repulsive forces
Two Types of Covalent Bonds
 Polar covalent bonds are covalent
bonds where electrons are shared
unequally between the atoms
 Non-polar covalent bonds are
covalent bonds where electrons are
shared equally between the atoms
Polarity
 Polarity depends on differences in
electronegativity
 The greater the difference in
electronegativity, the more polar the bond is
 Example: Cl2 and HF
 The more polar the bond, the stronger the
bond
 Polar covalent bonds have stronger bonds
than non-polar bonds
 Stronger bonds give higher boiling points
(just like ionic compounds)
The Chemical Bond Overview
 In order of increasing bond strength:
 In order of increasing bond length:
Naming Ionic Compounds
 Simple Naming Rules
 Identify the compound as Ionic
(Metal and a non-metal)
 Determine charges for each ion
 Overall charge of compound must
be zero
 General formula for names:
 Cation + Anion Root-ide
Examples
 Calcium fluoride
 Calcium phosphide
 Magnesium nitride
 Potassium oxide
Examples
 LiCl2
 SrBr2
 BaI2
Transition Metal Compounds
 Since transition metals form multiple ions, roman
numerals denote charge
Examples
 iron (III) chloride
 copper (II) oxide
 iron (III) oxide
 silver (I) sulfide
Polyatomic Ion Compounds
 Some elements are considered as a
charged group of two or more atoms.
They are considered as a single ion
called a polyatomic ion.
 You will not need to memorize these,
only recognize it when you see them
Examples
 Aluminum chromate
 Potassium hydroxide
 Sodium thiosulfate
 Calcium acetate