Block _________
Unit 7
Bonding Notes
•
Atoms are generally found in nature in combination held together by _______________
____________ .
•
A chemical bond is a _______________________________ between the nuclei and valence
electrons of different atoms that binds the atoms together
•
There are three main types of bonding: __________, ___________ and __________.
__________
•
Ionic Bonding occurs between a ______________ and a ______________.
•
Metallic bonding occurs between two ____________________.
•
Covalent bonding occurs between a ______________ and a ______________.
•
A positive ion is called a _____________________________.
•
A negative ion is called an_____________________________.
_____________________________.
What dete
determines the type of bond that forms?
•
The ______________________ of the two atoms involved are redistributed to the
___________________________________________
___________________________________________.
•
The interaction and rearrangement of the _______________________ determines which type
of bond that forms.
•
Before bonding the atoms are at their highest possible _______________________.
•
There are __________ philosophies of atom to atom interaction
interaction.
•
One understanding of the formation of a chemical bond deals with balancing the opposing
forces of _____________________________________.
-
•
Repulsion occurs between the _________________ clouds of each atom.
•
Attraction occurs between the __________________ and the negative electron clouds.
clouds
•
When two atoms approach each other closely enough for their electron clouds to begin to
overlap
•
The electrons of one atom begin to _______________
the
electrons of the other atom
•
And repulsion occurs between the _______________ of the two atoms
1
•
As the optimum distance is achieved that balances these forces, there is a release of potential
energy
•
The atoms _________________ within the window of maximum attraction/minimum repulsion
•
The _______________ released the stronger the _______________ bond between
bet
the atoms
•
Another understanding of the formation of a chemical bond between two atoms centers on
achieving the most __________________________ of the atoms’ valence electrons
•
By rearranging the electrons so that each atom achieves a ______________________
__________________
________________ ________________ creates a pair of stable atoms (____________
____________
___________________________________
___________________________________)
•
Sometimes
times to establish this arrange
arrangement
ment one or more valence electrons are ________
______________________________________________.
•
Basis for _________________ bonding
•
Sometimes valence electrons are _______________________________________
•
Basis for _____________________ bonding
•
A good predictor for which type of bonding will develop between a set of atoms is the
difference in their __________________________________________.
__________________________________________..
-
•
Remember, electro-negativity
negativity is a measure of the ______________________ an atom has for e
s after developing a bond
•
The _________________________ the difference between the two atoms, __________
___________________________________________________ of electrons
•
Let’s consider the compound Cesium Fluoride, _______________.
•
The electro-negativity
negativity value (EV
(EV) for Cs is ____________; the EV for F is ___________.
___________
2
•
The difference between the two is _____________,, which falls within the scale of ionic
character.
•
When the electro-negativity
negativity difference between two atoms is greater than
______________________________________
______________________________________.
•
•
The take home lesson on electro
electro-negativity and bonding is this:
-
-
The ________________________ are on the P.T., the more evenly their e interact, and are
therefore more likely to form a _______________________
-
•
The ________________________________ are on the P.T., the less evenly their e interact, and
are therefore more likely to form an ionic bond.
•
Hint - metal w/nonmetal = ionic
nonmetal w/nonmetal = covalent
3
Covalent Bonding
•
In a Covalent bond:
•
The ___________________________ between the atoms involved is not extreme
•
So the interaction between the involved electrons is ____________________________
•
It may not be an equal sharing relationship, but at least the electrons are being
“___________________”.
•
Covalent bonds are between _____________________________________________.
•
Covalent bonds are formed when electrons are _____________________ between two atoms.
•
If two atoms share 2 electrons, they form a _____________________________. If two atoms
share 4 electrons, they form a _____________________________.
If two atoms share 6 electrons, they form a ____________________________.
•
There are two types of covalent bonds: polar and non-polar. Polar bonds usually involve
__________________________________. Non-polar bonds usually involve
___________________________________.
•
In polar bonds, the electrons are shared ________________________________. In non-polar
bonds, the electrons are shared ________________________________.
•
Covalent compounds can exist in any state (solid, liquid or gas). They have _____________
melting and boiling points.
•
So what is the bottom line? To be stable the two atoms involved in the covalent bond share
their electrons in order to achieve the arrangement of a ________________.
Ionic Bonds
•
In an Ionic bond:
•
The electro-negativity difference is ____________________,
4
•
So the atom with the _______________________ pull doesn’t really share the electron
•
Instead the electron is essentially ___________________________________________
_______________________________________________________________________
•
When a metal bonds with a nonmetal, an
•
An ionic bond always involves the TRANSFER of electrons from the
to the
bond is formed.
.
•
The cation and anion are held together by ___________________________________.
•
An ionic compound does not consist of individual molecules. Instead, there is a huge network of
positive and negative ions that are packed together in a
.
•
Because their bonds are so strong, ionic compounds tend to have very
_________________ points.
•
Ionic compounds are _____________________________, which means they can conduct
electricity.
•
When forming ionic compounds the positive and negative charges must _____________.
•
_______________________________________________________________________
_______________________________________________________________________ .
•
An electron is _______________________ from the sodium atom to the chlorine atom.
•
The bottom line is, to be stable the two atoms involved in the ionic bond will either
___________________ or _________________ their valence electrons in order to achieve a
stable __________________ arrangement of electrons.
Metallic Bonding
•
Metallic bonds consist of positively charged metallic cations that donate electrons to the
__________________.
•
The “sea” of electrons are shared by all atoms and can move throughout the structure.
•
Properties:
o
o
o
o
Thermal Conductivity
Electrical Conductivity
Malleability- the ability to be hammered down into thin sheets.
Ductility- the ability to be drawn into a wire.
5
•
In a metallic bond:
•
The resulting bond is a cross between ____________ and _____________ bonding
•
Valence electrons are transferred from one metal atom to the __________________ metal atoms
•
But none of the involved metal atoms want the electrons from the original atom, nor their own so
they ___________________________________
•
What results is a ________________________________ of valence electrons that none of the
atoms in the collection ________________ the valence electrons
•
It resembles collection of positive ions floating around in a sea of electrons
6
Name ___________________________
Date _____________ Block ________
Rules of writing formulas:
•
•
•
•
· positive ion is written first … this is usually a metal
· negative ion is written second … this is usually a nonmetal
· subscripts are used to show how many ions of each part are in the compound. They are
used to balance the charge of the ions.
· criss-cross method:
Examples:
1.
sodium oxide
sodium is the positive ion = +1
oxide is the negative ion = -2
therefore … it takes 2 sodium ions to balance the charge of the oxide
Formula = Na2O
2.
calcium nitrate
calcium is the positive ion = +2
nitrate is the negative ion = -1
therefore … it takes 2 nitrates to balance the charge of calcium
Formula = Ca(NO3)2
3.
aluminum sulfide
aluminum is the positive ion = +3
sulfide is the negative ion = -2
therefore … it takes 2 aluminum ions and 3 sulfide to balance the charge
Formula = Al2S3
7
Write the correct formulas for each covalent compound:
Compound Name
Oxidation States
water
O (-2)
H (+1)
Carbon Dioxide
C (+4)
O (-2)
Chlorine (Diatomic Element)
Cl (-1)
Methane (5 total atoms)
C (-4)
H (+1)
Ammonia (4 total atoms)
N (-3)
H (+1)
Carbon tetrabromide (5 total
atoms)
C (+4)
Br (-1)
Phosphorous trichloride (4 total
atoms)
P (-3)
Cl (-1)
Diphosphorous trioxide (5 total
atoms)
P (-3)
O (-2)
Covalent Formula
Determining the Type of Bond:
Determine the type of bond (Ionic, Covalent or Metallic) in the following compounds:
Compound
NaCl
CO
FeNi
SiS2
Bond Type
Compound
NCl3
PF3
CaCl2
Fe2O3
Bond Type
8
Balancing Charges
Criss-Cross rule
1. Write out symbols and charge of elements
2. Criss-Cross charges as subscripts (Swap and Drop)
3. Combine as a formula unit
Equation Form of Balancing Charges
(Number of Cations)x(Cation Charge) + (Number of Anions)x(Anion Charge) = 0
(1)(+3) + (X)(-1) = 0, x = 3
o EX: Aluminum and Oxygen
•
EX: Barium and Oxygen
Balancing Charges Practice:
o Lithium Iodide
o Strontium Chloride
o Aluminum Nitride
o Sodium Sulfide
9
Bonds
VSPER- Valence Shell Electron Pair Repulsion
Lone Pairs
Shape
Linear
Bent
Trigonal Planar
Trigonal Pyramidal
Tetrahedral
Steric number is the total number of ______________________________ AND
______________________.
10
VSEPR Practice
Complete the table with the requested information.
Molecule
Structural Diagram
Oxidation State of
each element
Molecular
Geometry
CClF3
SF2
BF3
SiBr4
NH3
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Polarity
Bond Polarity
Electronegativity
Ionic bonds have an electronegativity difference that is greater than 1.7. Covalent bonds have
an electronegativity difference less than (or equal to) 1.7. Electronegativity differences
between 0 and 0.4 indicate non-polar covalent bonds. Electronegativity differences between
0.4 and 1.7 indicate polar covalent bonds.
Polar Covalent Bond- a covalent bond in which the electrons are not shared equally because
one atom attracts them more strongly than the other.
Non-polar Covalent Bond- a covalent bond in which the electrons are shared equally.
Use the periodic table of electronegativities to answer the questions on electronegativity
differences.
H
2.1
Li Be
1.0 1.5
ELECTRONEGATIVITY
(electron attraction!)
Na Mg
0.9 1.2
B C N O F
2.0 2.5 3.0 3.5 4.0
Al Si P S Cl
1.5 1.8 2.1 2.5 3.0
K Ca
0.8 1.0
Sc
1.3
Ti V Cr
1.5 1.6 1.6
Mn
1.5
Fe Co Ni Cu Zn Ga Ge As Se Br
1.8 1.9 1.9 1.9 1.6 1.6 1.8 2.0 2.4 2.8
Rb Sr
0.8 1.0
Y
1.2
Zr Nb Mo
1.4 1.6 1.8
Tc
1.9
Ru Rh Pd Ag Cd In Sn Sb Te I
2.2 2.2 2.2 1.9 1.7 1.7 1.8 1.9 2.1 2.5
Cs Ba La-Lu Hf Ta W
0.7 0.9 1.0-1.2 1.3 1.5 1.7
Re
1.9
Os Ir Pt Au Hg Tl Pb Bi Po At
2.2 2.2 2.2 2.4 1.9 1.8 1.9 1.9 2.0 2.2
Fr Ra
0.7 0.9
Ac
1.1
Th Pa U Np-No
1.3 1.4 1.4 1.4-1.3
12
Determine the type of bond that would form between the following two elements using
differences in electronegativity.
Example: Mg – O
O is 3.5 and Mg is 1.2, therefore, the difference is 3.5 – 1.2 = 2.3 IONIC
Example: Cl – Cl
Cl is 3.0. The difference is 3.0 – 3.0 = 0
NON-POLAR COVALENT
Bond
Electronegativity Difference
Bond Type
1. C – N
2. Li – F
Bond
Electronegativity Difference
Bond Type
3. N – Cl
4. Na - Cl
5. O – F
6. B – H
7. Ba – F
8. C – H
Molecular Polarity
Dipole moment- a property of a molecule whereby the charge distribution can be represented
by a center of positive charge and a center of negative charge.
Polar Molecule- a molecule that has a permanent dipole moment.
Determining if a molecule is polar.
1. If ALL of the bonds are non-polar, then the molecule is non-polar.
2. If some or all of the bonds are polar, you can consider the vectors. Vectors are arrows
that point in the direction of the negative charge (the direction the electrons are
pulled). Examples:
O
POLAR
H
H
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a. If all the arrows point toward the central atom AND the central atom has lone
pairs, then the atom is polar.
H
NON-POLAR
H
C
H
H
b. If all the arrows point toward the central atom AND the central atom has no lone
pairs, then the atom is non-polar.
H
F
POLAR
c. If the arrow points toward one atom in a linear molecule, it is polar.
d. If the arrows all point away from the central atom AND there are no lone pairs
on the central atom, then the atom is non-polar.
e. If the arrows all point away from the central atom AND there are lone pairs on
the central atom, then the atom is polar.
3. Another way to determine if a molecular is polar or not, is to look at symmetry.
H
NON-POLAR
H
C
H
O
C
O
H
a. If the molecule is symmetrical, then the molecule is non-polar.
b.
H
H
C
H
F
POLAR
H
Cl
c. If the molecule is not symmetrical, then the molecule is polar.
d. If the molecule is bent or trigonal pyrimidal, then the molecule is polar (lone
pairs on the central atom mean that it is polar).
14
Draw the structural formula for each molecule, and determine if it is polar or non-polar.
Formula
Structural Formula
Polar/Non-polar
NH3
SCl2
CF4
PCl3
H2 S
C 2 H2
15
Bonding and Shape Quiz Review
Determine the formula for the compound formed by the two atoms and indicate
if it is an ionic or covalent compound
1. Calcium and Oxygen
2. Nitrogen and Fluorine
3. Sodium and Chlorine
4. Carbon and Oxygen
Draw the dot diagram for each of the IONIC compounds below
5. CaO
6. Na2S
10. KI
7. SrF2
Complete the table below.
Formula
Electron Dot
Diagram
Bonding
Orbitals
Shape
Structural Formula
Polar?
NCl3
CO2
H 2O
CH3F
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