Chemical Bonding
Formation of Ions and Types of Bonds
Ions: an atom that has a positive or negative
charge, as a result of gaining or losing electrons
Cation: an atom with a positive charge, resulting
from the loss of valence electrons
Anions: an atom with a negative charge, resulting
from the gain of valence electrons
•Loss of electrons is Oxidation
•Gain of electrons is Reduction
The Octet Rule
Atoms react by gaining or losing electrons to acquire the stable electron
structure of a noble gas, usually 8 valence electrons.
An atom is unstable when its valence electron shell is not full.
An unstable atom will react with others, becoming an ion
Changes the # e- to get more stable
Noble gases have a full octet of 8 valence electrons
*except He (2e- )
They are very stable and do NOT react with other elements
Number of valence electrons
Charge of ions
# electrons
# valence
lost or
electrons
gained
Potassium
Bromine
Phosphorus
Gallium
Cation
Or
Anion
Oxidation
Number
Ion
Symbol
Bond: force that holds groups of 2 or more atoms together in
a compound
•
usually consist of 2 or more elements
***ALL BONDING has to do with an atom’s
ELECTRONS and how they are used
Electrons can be transferred, shared or loose
between atoms
Three Types of Bonds
1)Ionic
2)Covalent
3)Metallic
Ionic Bond
Ionic bonding occurs when electrons are transferred between atoms.
Metals react with nonmetals
to form ionic compounds.
Elements in Ionic Compounds
Metals – cations (+)
Nonmetals – anions (-)
The bond that holds oppositely charged
particles together in an ionic compound.
Covalent Bonds
Occurs when electrons are shared between 2
atoms
Nonmetals react with other nonmetals (or
metalloids) to form a covalent compound.
Two types of Covalent Bonds:
2a) Nonpolar Covalent – occurs when electrons
are shared equally between two atoms.
2b) Polar Covalent – occurs when electrons are
shared unequally between two atoms.
Metallic Bonds
Metallic bonds: forces of attraction between the free-floating valence
electrons and the positively charged metal ions.
A GROUP of METAL atoms,
closely packed (positive ions)
with loosely held valence
electrons.
Type of Bond? - Ionic, Covalent, Metallic ?
Formula
TiO2
CH4
CS2
KCl
H2
1st Element:
Metal/Nonmetal
2nd Element:
Metal/Nonmetal
Type of Bond
Practice – Formation of Ions/ Types of
Bonds
Naming and
Formulas:
Binary Ionic
Compounds
Including
Transition
Metals
Binary: contains 2 types of elements
Compound: group of chemically combined
elements, have new properties
Rules for Naming Binary Ionic Compounds
1) Name the metal (cation) first
2) Name the nonmetal (anion) second,
change the ending to – ide
AlBr3 ______________________________
Ba3N2 ______________________________
Let’s Do a Few More
K2O ______________________
CaI2 _______________________
Li3P _______________________
Compare the following formulas
NaCl
Na2S
In order to balance an ionic formula:
Cation charge (+) MUST balance by adding up to zero!
Compounds are electrically neutral (net charge = 0)
Rules for Writing Formulas for
Binary Ionic Compounds
1) Write each element’s symbol
Magnesium and
2) Determine the charge for
each element (from oxidation sheet)
3) Balance out the charges
(Crisscross)
4) Rewrite the formula (without the charge/signs)
SIMPLIFY if possible!
Nitrogen
Potassium phosphide
Calcium sulfide
Writing Binary Ionic Compounds with
Transition Metals
What is the problem with writing formulas for ionic compounds
with transition metals?
Because transition metals can form more than one (+) ion
• (has more than 1 oxidation # - colored in on our oxidation sheet)
How do you determine the charge for a transition metal?
Use a roman numeral to indicate which charge is used
*(This does NOT mean the # of atoms)
Copper (I) chloride
Copper (I) sulfide
***Watch what happens if I change the roman numeral
Copper (II) chloride
Copper (II) sulfide
Naming Binary Ionic Compounds with
Transition Metals
1) Determine the charge of the ions
2) Name the metal (cation) first
3) Write the charge of the cations as a
Roman numeral in ( )
4) Name the nonmetal (anion), change
ending to - ide
HgSe
Fe2O3
TiCl4
Ag2O
NiN
Practice – Binary Ionic Compounds
including Transition Metals
Naming and Formulas: Ionic with Polyatomic
Ions
What is a polyatomic ion? Tightly bonded group of atoms
that behave as a single unit with a single charge
Draw a diagram of the following polyatomic ions:
Nitrate ion: NO3-1
Hydroxide ion: OH-1 Sulfate ion: SO42-
Acetate ion: C2H3O2-1
Ammonium ion: NH4+1
What does the suffix “-ate” mean?
What does the suffix “-ite” mean?
Examples:
Nitrate NO3
Nitrite NO2
Sulfate SO4
Sulfite SO3
Rules for Naming Ionic Compounds with
Polyatomic Ions
1) Name the metal (cation +) first
2) Name the anion (-), no need to change ending if
ion is a polyatomic ion **single NM – ide
NaNO3
Mg(OH)2
K2CO3
NH4Cl
Ag2SO3
Fe(HCO3)3
NaOH
(NH4)2CO3
Rules for Writing Formulas for Binary Ionic
Compounds
1) Write each element’s symbol
2) Determine the charge for each element or
Cesium sulfate
polyatomic ion
3) Balance the charges (crisscross)
4) Rewrite the formula (w/o the charge/sign) Magnesium
phosphate
Aluminum permanganate
Copper (I) sulfate
Iron (III) acetate
Ammonium nitride
Practice – Ionic Compounds with Polyatomic
Ions
Practice – Naming and Formulas for ALL
Types of Ionic Compounds
Quiz #6 – Naming and Formulas for
Ionic Compounds
Naming and Formulas: Covalent Compounds
Binary covalent (molecular) compounds contain
nonmetals and nonmetals/metalloid
What are prefixes for? Tells how many - #
atoms of each element in the compound
Name the prefixes for the following numbers
1
2
3
4
5
6
7
8
9
10
Rules for Naming Covalent Compounds
1) Name the first nonmetal
Add prefix
** Never use mono – on the first NM
2) Name the second NM
Drop ending, add – ide
Add prefix
*** Prefixes and subscripts MUST match
CO2
P2O5
SO2
CCl4
SF6
As2O3
Exceptions:
Scientific
Name
Common
Name
H2O
NH3
CH4
Rules for writing formulas
1) Write each element’s symbol
2) Turn prefix for each element into a
disulfur trioxide
number and write it as the
subscript
phosphorus pentachloride
dinitrogen monoxide
heptacarbon diphosphide
What are diatomic molecules?
2 atoms of the same element, that are
naturally found bonded together (NOT when
bonded with another element)
** remember from Unit 0
Formula
Name
Practice – Covalent Compounds
Practice – Properties of Ionic and
Covalent Compounds
Practice – Naming and Formulas: Ionic or
Covalent?
Quiz #7 – Ionic and Covalent:
Properties, Naming and Formulas
Naming and Writing Formulas: Acids
An acid is a certain type of molecular compound.
You can recognize an acid because ALL acid
formulas start with H (charge will always be +1)
Binary acids: only have 2 elements, H and a nonmetal
Name always starts with prefix Hydro
Ternary (oxyacids) acids: have H and a polyatomic ion
The names of acids depend on the type of anion they
contain (also by how many elements they contain)
Binary – 2
Ternary – 3 or more
If the anion ends with- the acid name will end
with - ide the name will end with – ic
- ate the name will end with – ic
- ite the name will end with – ous
For example: sulfate  sulfuric
nitrite  nitrous
Formula
HBr
H3PO4
HClO2
HNO2
Anion
Anion name
Acid Name
Type of Acid
(B / T)
Name
Sulfuric acid
Hydrofluoric
Acid
Nitrous acid
Oxalic acid
Anion
Formula
Anion Name Acid Formula Type of Acid
(B/T)
Writing Formulas: Hydrocarbons
Hydrocarbons contain only Hydrogen and Carbon
Named using prefixes (similar to covalent)
Ending comes from the series
Series
--- ending
General
Formula
Alkane
CnH2n
yne
Compound
Name
Methan
Decyne
Butene
Formula
C6H12
C2H6
Series
Quiz #8 Acids and Hydrocarbons: Properties,
Naming and Writing Formulas
Lewis Structures: The Basics
Lewis Structures
A diagram representing a covalent molecule
Shows all atoms and all valence electrons, bonded and non-bonded
Lone pairs
Steps to Draw a Lewis Structure
1) Count total number of valence electrons
2) Arrange atoms (element with highest electronegativity or
element with least # of atoms, goes in the middle, )
3) Single bond everything
• Subtract bonding electrons from total (1 bond = 2 electrons)
4) Count number of electrons needed to complete octets
• If you have enough, add dots
Example: H2O
OBr2
NH3
CH4
C3H8
Lewis Structures of Polyatomic Ions
Negative ion (anion): add electrons (*gains electrons)
Positive ion (cation): subtract electrons (*losses electrons)
Place entire dot structure in [ ] and put charge as exponent
SO42-
NH41+
Lewis Structures: Multiple Bonds, Resonance
and Exceptions
Rules for Lewis Dot Structures Revised
1) Count all valence electrons
2) Arrange atoms
3) Single bond everything, subtract bonding electrons from total (1 bond =
2 electrons)
4) Count number of electrons needed to complete octets
For every TWO electrons short, make a multiple bond
• First double bond, then triple bond
• Keep molecules symmetrical if possible
• DO NOT put multiple bonds on Hydrogen
5) Recount # of electrons needed to complete octets
• If you have enough, add dots
O2
CO
CO2
Resonance
When there is more than one valid Lewis Structure
Location of the double bond can be different as long as it is between the
SAME two elements
SO3
HCO31-
Exceptions
Boron
Electron deficient
(6)
BF3
Phosphorus and below
expanded octet
(10)
PCl5
Sulfur and below
expanded octet
(12)
SF6
Go over Shapes of Molecules
Worksheet Molecular Shapes
Practice – Lewis Structures: Multiple Bonds,
Resonance and Exceptions
Quiz # - Lewis Structures
Polarity
Electronegativity
Ability of an atom, bonded to another atom, to attract
electrons to itself
* F highest
Fr lowest
Ionic Compound
Transfer of 1 or more
valence electrons
Polar Covalent
Compound
Electrons shared
unequally between 2
atoms
Form ions
Nonpolar Covalent
Compound
Electrons shared equally
between 2 atoms
No charges
Partial charges
Na1+
Cl1_
Cl
H
Electronegativity
Difference > 2.0
Cl
Cl
Electronegativity
Difference 0.5 – 2.0
Electronegativity
Difference < 0.5
Bond Polarity
To determine bond polarity, find the electronegativity difference
between the two atoms involved
EN difference (ΔEn) = I EN of 1st element - EN of 2nd element I
B and Cl
S and Se
KBr
Cl2
CH4
Which side of a polar bond is partial positive (δ+) and
which is partial negative (δ-) ?
Low EN
ee-
–
δ
+
δ
High
EN
Identify if the bond is polar or nonpolar, then identify
which atom is δ+ and δCl - H
S-O
P - Cl
Dipole
A molecule that has two electrically charged regions, or poles
Polar Molecule
Molecule with a dipole OR electrons shared unequally
What may cause a molecule to be polar?
Polar bonds OR Lone pair electrons on center atom
Generally includes what shapes of molecules?
Linear
Bent
Trigonal Pyramidal
Nonpolar Molecule
Molecule that does NOT have a dipole
Electrons are shared equally
What may cause a molecule to be nonpolar?
Nonpolar bonds
Symmetrical shape
Generally includes what shapes of molecules?
Diatomic molecules
Trigonal planar
Linear w/ 3 atoms
Tetrahedral
Identify the molecular polarity of the
following compounds:
CCl4
CO2
PCl3
H2O
Practice – Polarity
Quiz #11 - Molecular Shapes and Polarity