Transcript Bonding Notes

Unit 4
Chemical
Bonding
Why chemical bonds form?
• It takes energy to
separate atoms that are
bonded together.
• The same energy is
released when chemical
bonds form.
• Atoms form bonds to
reach a lower energy
state.
A chemical
bond forms
when atoms
transfer or
share valence
electrons.
Valence electron are what get transferred
or shared to form the chemical bond
Forming Chemical
• Octet Rule
Atoms will form
Bonds
bonds by:
– Sharing
– Giving or
– Taking
electrons to
complete
their octet
Or be like a
Noble Gas
Higher energy farther away from nucleus
Forming Chemical Bonds
• Lithium
–Better to lose 1 electron or
to gain 7 electrons?
X
Ionization
• Neutral element: # protons = # electrons
-wants to lose an e’
Na
1+
- wants to gain an e’
Cl
1-
OXIDATION #s
Oxidation Numbers
- indicate # of
e’ lost or
gained
PRACTICE:
2
Oxygen
+
1
1
Potassium
Fluorine
What is the oxidation number
for sulfur?
1+
2+
3+
0
1230%
3-
0%
2-
0%
1-
0%
0
0%
3+
0%
2+
0%
1+
1.
2.
3.
4.
5.
6.
7.
What is the oxidation number
for aluminum?
1+
2+
3+
0
1230%
3-
0%
2-
0%
1-
0%
0
0%
3+
0%
2+
0%
1+
1.
2.
3.
4.
5.
6.
7.
What is the oxidation number
for all halogens?
1+
2+
3+
0
1230%
3-
0%
2-
0%
1-
0%
0
0%
3+
0%
2+
0%
1+
1.
2.
3.
4.
5.
6.
7.
What is the oxidation number
for all noble gases?
1+
2+
3+
0
1230%
3-
0%
2-
0%
1-
0%
0
0%
3+
0%
2+
0%
1+
1.
2.
3.
4.
5.
6.
7.
PRACTICE
• Mg
• Fe (III)
• Cl
•S
• Be
+
2
+
3
1
–
2
+
2
–
• Cu (II)
• Br
• Na
• Cu (I)
•N
+
2
1
1
+
1
_
3
+
Ionic Bonds
NaCl - salt
+
• Forms between a metal and nonmetal
• Atoms LOSE or GAIN its valence electrons
• ve’ are transferred from one element to
another
Covalent Bond
• Forms between 2 nonmetals
• Atoms SHARE electrons
– H wants to give an e’
– O wants to take 2 e’
– SHARE between
– highest energy level.
DIATOMIC MOLECULES H2
• Covalent molecules that like to bond
with atoms of the same type
N2
F2
O2
I2
Cl2
“Have No Fear Of Ice Cold Beverages”
Br2
Ionic
Covalent
• Gain / Lose e’
• 2 opposite
charged ions
• Bonds between
metals and
nonmetals
• Compound
•Share e’
•2 same charged elements
•Bonds between 2
nonmetals
•Molecules
Why do Atoms form Bonds?
Are most atoms stable?
Electronegativity
• Electron pairs in covalent bonds may be
shared unequally.
– Strong electronegativity pulls the e’ more towards
one atom
– Group 17 (VII) strong electronegativity
– Group 1 (I) weak electronegativity
Copper
Atom
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
The Atom
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
C
Cu
Cu
Cu
C
Cu
Metallic Bond
• Formed between atoms of metallic
elements
• Electron cloud around atoms
• Good conductors at all states, lustrous,
very high melting points
• Examples; Fe, Al, Au, Co
Metallic Bond
A Sea of Electrons
Metals Form Alloys
Metals do not combine with metals.
They form alloys.
- which is a solution of a metal in a metal
Examples: steel, brass, bronze and
pewter.
Identify the type of bonding in
the following substance: KBr
1. Ionic
2. Covalent
3. Metallic
lic
0%
M
et
al
en
t
0%
Co
va
l
Io
ni
c
0%
Identify the type of bonding in
the following substance: Fe
1. Ionic
2. Covalent
3. Metallic
lic
0%
M
et
al
en
t
0%
Co
va
l
Io
ni
c
0%
Identify the type of bonding in
the following substance: CuCl
1. Ionic
2. Covalent
3. Metallic
lic
0%
M
et
al
en
t
0%
Co
va
l
Io
ni
c
0%
Identify the type of bonding in
the following substance: NO2
1. Ionic
2. Covalent
3. Metallic
lic
0%
M
et
al
en
t
0%
Co
va
l
Io
ni
c
0%
Learning Check
• Identify the following as Ionic,
Covalent or Metallic
• LiBr
• FeCl3
• CO
• Steel
Ionic
Ionic
Covalent
Metallic
Na3N Ionic
CaBr2 Ionic
Cu Metallic
NO2 Covalent
Chemical Formulas – Ionic Compounds
• Transition Metal
• Iron (III) + Oxygen
• Fe 3+
Fe
O 2- =
+
O
= Fe2 O3
• Criss-cross the oxidation #s not the + or- signs
Solving Problems
• Iron and oxygen combine to form a
compound. Iron (Fe) has an oxidation
number of 3+. Oxygen (O) has an
oxidation number of 2–.
• Predict the chemical formula of this
compound.
Solving Problems
1. Looking for:
–
…formula for a binary compound
2. Given
–
… Fe3+ and O2–
3. Relationships:
–
Write the subscripts so that the sum of the oxidation
numbers equals zero.
4. Solution
–
–
Two iron atoms = 2 × (3+) = 6+
Three oxygen atoms = 3 × (2–) = 6–
Solving Problems
3+
Fe
3 x
2-
O
2
=
6
Solving Problems
3+
2-
Fe
O+
+
O+
3+
Fe
=
+6
2-
+6
-6
0
2-
O
=
-6
Solving Problems
3+
2-
Fe2 O 3
Naming Ionic Bonds
• Must be - metal + nonmetal
• Given Formula
– Write the name of 1st element
– Write the name of the 2nd element – but
change end to “ide”.
• Given Name
– Write the Ox #’s above each element
– Write the chemical symbol of each
element
– Criss-Cross the oxidation numbers
Naming Covalent Bonds
• Must be - nonmetal + nonmetal
• Given Formula
– Look at the subscript for each element
– Use the Greek prefix to show the #
• “mono not necessary on 1st element, but is on 2nd
– Change the ending of the 2nd element to “ide”
• Given Name
– Use the Greek prefixes to determine the
subscripts for each element.
– Write the chemical symbol then subscript.
Naming Ionic Compounds
• Simple Ionic
– Name first element
– Root name of 2nd
element (change “ine”
to “ide”
– Ex: NaCl
• Sodium + chlorine
• = sodium chloride
Naming Covalent Compounds
•
•
•
•
•
• Prefix
AKA molecular
 monocompounds
 di Binary Compounds –
 tri have only 2 elements
 tetra Name the + ion
 penta Name the – ion (change
“ine” to “ide” AND give the  hexa # of atoms
 hepta
Ex: CO – carbon monoxide
 octa
 nona -
Meaning
1
2
3
4
5
6
7
8
9
Formulas
• Empirical
– Simplest whole #
ratios by which the
elements combine
• Ex: CH2O
• Molecular
– The actual # of atoms of
each element in the
compound
• Ex: 6 x CH2O ---C6H12O6
How many carbon atoms?
Hydrogen?
Oxygen?
Compounds Vs Mixtures
• Compounds
• Mixtures
– Chemical bonds
– Just are placed
hold the atoms
together
or ions together
– same # of atoms
– Can vary
or ions
– elements
– Can Vary
proportional