Ionic and Covalent Bonding - Fall River Public Schools
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Transcript Ionic and Covalent Bonding - Fall River Public Schools
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