Chapter 5 B

http://emp.byui.edu/StevensN/Chapter5b.
p
pt
Chapter 5
Chemical Bonds
Some Definitions
Valence electrons
Octet Rule
Ion
Cation
Anion
Electronegativity
Polarity
Ions on the Periodic Table

CATION
+1 +2
CATION Non-Ionic
ANION
+3 ? -3 -2 -1 ?
Electron-dot structures
Also called Lewis Dot Structures

Represent an elements valence electrons
Representative of the valence electrons for
the entire group
Features:
1. Each electron is represented by a dot
surrounding the atomic symbol of an element
2. Dots are only allowed in 4 positions (top,
bottom, left, right), no in-betweens
Electron-dot structures
What is the electron-dot structure for

sodium?

oxygen?

neon?
Practice
Write the electron-dot symbols for a sodium
metal atom and a chlorine atom, and their
ions.
Na
Na
Cl
+
Cl
Ionic Bonding
Sodium Chloride
Ionic Bonding
Atoms shuffle electrons, then are attracted to

each other because of net charge
=
IONIC BOND
Formulas of Ionic Bonding
Textual way of describing what is physically happening

Ions come first, then attraction of charges = BALANCE
Writing Ionic Formulas

Write the formula for calcium fluoride.
Write the symbols for the ions, and their
charges.
Cross over the charge numbers so they
become subscripts.
Rewrite the formula, dropping the charge
superscripts.
2+
1
Ca
FCaF2
12
Naming Ionic Compounds
Between 2 Elements
1. Name of metal ion
2. Name of non-metal ion, ide suffix
Those Pesky Transition Metals
Chromium Cr2+
chromium(II)
3+
Cr
chromium(III)
Variable valence =+ we cannot
predict ionic
Copper
Cu
copper(I)
charge from the Cu
group
number
2+
copper(II)
2+
Iron
Fe
iron(II)
Roman numeral in3+ parenthesis
is used to
Fe
iron (III)
indicateManganese
ion
Mn2+
manganese(II)
Mn3+
manganese(III)
Nickel
Ni2+
nickel(II)
Ni3+
nickel(III)
Zinc
Zn2+
zinc(II)
Naming Ionic Compounds

Write the name for ZnCl2
1. Cross over the subscripts so they become
charges
Remember that the metal (positive ion) is

always first.
2. Write the name of each element and add

ide ending to the non-metal
3. Be sure to include a roman numeral in
parenthesis if the metal is a transition
element
Practice
React lithium and sulfur together. What will
happen?
Li
Li
S
+
Stable?
2-
Li
2Li+ + S2- = Li2S
Bond, Chemical Bond
Ionic Bonding
1. Electron transfer from metal to non-metal
2. The more electronegative atom wins!
Covalent Bonding
1. Electron sharing between non-metals
2. Atoms of similar electronegativity
Covalent Bonding
2 Atoms share valence electrons to create
stable bonds
No transference of electrons
Between atoms of similar electronegativity
Non-metals
Atoms seeking to fill an octet: achieve the
next highest noble gas configuration
Naming Covalent
Compounds
First non-metal = elemental name
Second non-metal = elemental name with
ide ending
E.g. oxide, sulfide, bromide
Subscripts = use prefixes to name multiple

atoms
Exception: for oxygen, drop the a at the
end of the prefixes
E.g. tetroxide, hexoxide, pentoxide
Example
Name the following covalent compound
N2O3
dinitrogen trioxide
C Cl4
* carbon tetrachloride
* By convention, the mono- on the first

atom is not generally included
Example
Write the formula for the following
compound:
tetraphosphorus hexoxide
4 Ps
6 Os
P4O6
Electron-dot Formulas
1. Determine the arrangement of atoms
For central atom(s), it will generally be single,

surrounded by multiple other atoms
2. Determine the total number of valence electrons

3. Attach the central atom to each bonded atom by
an electron pair
Represented by a dash
4. Arrange the remaining electrons around the outer

elements first, then the central atom
5. If octets are not complete, form a multiple bond
Practice
Draw the electron-dot formula for nitrogen
tribromide
No multiple bonds necessary!
Br N Br
Br
Practice
Draw the electron-dot formula for carbon
dioxide.
Multiple bonds necessary!
O C O
Diatomic Molecules
Several non-metals are naturally diatomic:
more stable electron configuration
Oxygen and nitrogen form multiple bonds
to achieve stability
N
N
N N
Polyatomic Ions
A group of atoms with a net electrical charge
Most are non-metals covalently bonded to

oxygen
Net charge: -1, -2, -3 shared among the atoms
Two notable exceptions are +1:
1. Ammonium (NH4+)
2. Hydronium (H30+)
Formed when a larger molecule splits

unevenly
Names of Polyatomic Ions

Memorize the common ate ions
Nitrate
Chlorate
Bromate
Carbonate
Sulfate
Phosphate
NO3ClO3BrO3CO32SO42PO43-
Remember these exceptions!

hydroxide OHammonium NH4+
hydronium H3O+
Add an O = per- prefix on ate ion (e.g. perchlorate, ClO4-)

Lose an O = -ate changes to ite (e.g. chlorite, ClO2-)
Lose another O = hypo- prefix on ite ion (e.g. hypochlorite,
ClO-)
All forms (-ate, -ite, per- hypo-) of an ion have

the same charge!
Naming Polyatomic Ions

Recognize the polyatomic ion as a UNIT
Name the metal ion first, then the polyatomic
ion
No extra prefixes or suffixes
Ca CO3
Calcium Carbonate
VSEPR Models
Based on several assumptions:

1. Atoms in a molecule are bound together by at least
one pair of electrons: a bonding pair
2. Some atoms may possess unbound, or lone pair,
electrons
3. Arrangements of electrons in the molecule will
minimize electron interactions
4. Lone pairs occupy more space than bonded pairs
5. Double bonds occupy more space than single
bonds
6. Multiple bonds are considered as single bonds
when determining molecule shape
VSEPR Models
Electron group geometry vs. Molecular

geometry (shape)
Electron group geometry = placement of electrons

around the central atom
Molecular geometry = 3-dimensional arrangement
of the molecule
Electron group geometry determines shape

Shape only refers to atoms and bonded
electron groups, not lone pairs
Points to Remember
1. ONLY the number of electron groups that
surround the central atom are considered in
determining molecular shape
2. 1 electron group may consist of a triple bond, a
double bond, a single bond, or a lone pair
3. A lone pair will give a different molecular shape
than a single, double, or triple-bonded atom at
the same position
VSEPR Models
Electron
Pairs
Bonded
Pairs
Lone Pairs
Molecular
Geometry
Examples
Linear
CO2
O =C =O
CO2
Source: http://www.molecules.org/VSEPR_table.html
VSEPR Models
Electron
Pairs
Bonded
Pairs
Lone Pairs
Molecular
Geometry
Example
Bent 120
NO2-
N
O
NO
VSEPR Models
Electron
Pairs
Bonded
Pairs
Lone Pairs
Molecular
Geometry
Example
Triangular
(Planar)
NO3CO32-
O
N
NO
VSEPR Models
Electron
Pairs
Bonded
Pairs
Lone Pairs
Molecular
Geometry
Example
Bent
109.5
H2O
H
O
H2 O
VSEPR Models
Electron
Pairs
Bonded
Pairs
Lone
Pairs
Molecular
Geometry
Example
Pyramidal
NH3
NH3
N H
H
VSEPR Models
Electron
Pairs
Bonded
Pairs
Lone
Pairs
Molecular
Geometry
Example
Tetrahedral
CH4
H
H
CH4
C H
H
Electronegative Atom
Monster
Electronegativity
increases
Predicting Bond Type
Source: http://www.chem.ufl.edu/~chm2040/Notes/Chapter_11/writing.html
Polarity
Is a BOND polar or non-polar?
Is a MOLECULE polar or non-polar?
Be careful! Polar bonds can make a nonpolar molecule!
Bond =
non-polar
Cl Cl
Molecule =
non-polar
Polarity
Opposing dipoles cancel!
Bonds =
polar
O=C=O
Molecule =
non-polar
Polarity
Dipoles do not cancel!
Bonds =
polar
Molecule =
polar
Between Molecules: Hydrogen Bonds
Hydrogen attached to highly electronegative atoms

F, O, N
Strong dipoles
Attraction of opposite dipoles
http://images.google.com/imgres?
imgurl=http://polymer.bu.edu/~fstarr/net.jpg&imgrefurl=http://polymer.bu.edu/~fstarr/water.html&h=248&w=350&sz=17&tbnid=4GT8aTZv8MkJ:&tbnh=82&tbnw=116&hl=en&start=49&prev=/images%3Fq
How Plants Work
Source: http://www.agridept.gov.lk/Techinformations/Hponics/images/P_24.jpg
Source:http://upload.wikimedia.org/wikipedia/en/thumb/c/c8/Coastredwood.jpg/250px-Coastredwood.jpg
Hydrogen Bonding at our Core
Source:http://colossus.chem.umass.edu/chandler/ch112/dna_hbond.gif
Between Molecules: Dipole-Dipole

Different nonmetals bonded
together
Partial charges:
Dipoles
Attraction of
opposite dipoles
http://images.google.com/imgres?imgurl=http://library.tedankara.k12.tr/chemistry/vol2/dipole-dipole%2520forces/z105.jpg&imgrefurl=http://library.tedankara.k12.tr/chemistry/vol2/dipole-dipole
%2520forces/z105.htm&h=570&w=409&sz=65&tbnid=ljWYJbTg9PEJ:&tbnh=131&tbnw=93&hl=en&start=2&prev=/images%3Fq%3Ddipole-dipole%26svnum%3D10%26hl%3Den%26lr%3D%26rls
%3DGGLC,GGLC:1969-53,GGLC:en
Between Molecules: Dispersion

Non-polar
molecules
Temporary dipoles
because of nonuniform electron
cloud (not
dispersed evenly)
Weak bonds
Source: http://touregypt.net/vdc/slide.86.jpg
To Sum Up the Forces
Practice
For your molecule, determine:
Name
Electron-dot structure
3-dimensional structure
VSEPR shape
Intramolecular force
Intermolecular force

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http://emp.byui.edu/StevensN/Chapter5b.

Ions on the Periodic Table

Also called Lewis Dot Structures

What is the electron-dot structure for

What is the electron-dot structure for

What is the electron-dot structure for

Atoms shuffle electrons, then are attracted to

Formulas of Ionic Bonding

Textual way of describing what is physically happening

Writing Ionic Formulas

Naming Ionic Compounds

Those Pesky Transition Metals

Naming Ionic Compounds

Remember that the metal (positive ion) is

2. Write the name of each element and add

2Li+ + S2- = Li2S

Bond, Chemical Bond

Subscripts = use prefixes to name multiple

* By convention, the mono- on the first

For central atom(s), it will generally be single,

2. Determine the total number of valence electrons

4. Arrange the remaining electrons around the outer

No multiple bonds necessary!

Multiple bonds necessary!

A group of atoms with a net electrical charge

Most are non-metals covalently bonded to

Formed when a larger molecule splits

Names of Polyatomic Ions

Remember these exceptions!

Add an O = per- prefix on ate ion (e.g. perchlorate, ClO4-)

All forms (-ate, -ite, per- hypo-) of an ion have

Naming Polyatomic Ions

Based on several assumptions:

Electron group geometry vs. Molecular

Electron group geometry = placement of electrons

Electron group geometry determines shape

Predicting Bond Type

Between Molecules: Hydrogen Bonds

Hydrogen attached to highly electronegative atoms

How Plants Work

Hydrogen Bonding at our Core

Between Molecules: Dipole-Dipole

Between Molecules: Dispersion

To Sum Up the Forces

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