PP 15: Bonding
Drill: Calculate the volume of hydrogen gas produced at -23oC under 83.1 kPa pressure when
3.4 g of ammonia is decomposed.
Bonding
Types of Bonds:
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Ionic
• Electrons are transferred from one atom to another creating (+) & (-) ions
• Metal & nonmetal
Covalent
• Electrons are shared by two atoms
• Two nonmetals
• Weaker than ionic
Metallic
• Electrons are shared by many atoms
• Electrons free to move
• Two or more metals
Characteristics of the types of compounds:
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•
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Ionic compounds
• Held together by electrostatic charge
• Very high MP
• Brittle
Covalent compounds
• Low MP
• Two nonmetals
• Flexible
• Some exceptions
Metallic substances
• Generally high MP
• Hard & lustrous
• Less brittle
• Conductors
Network Covalent or Macromolecules: VHMP & extremely hard
Molecule: Any covalent compound that can exist as an entity by itself
Distinguishing Bond Types: Distinguishing ionic & covalent bonds can be difficult, but generally
determined by differenceelectronegativity
Because we will not deal with metallic bonds, the types we will be studying are:
Ionic, Polar Covalent, & Non-Polar Covalent
Coordinate Covalent Bonds: A covalent bond in which the two electrons are donated by one atom
Dipole: A polar bond or a polar molecule (any entity that is polar)
H-F
+
-
Ionic Bonds: Electrostatic attraction between positive & negatives charges
F = kq1q2/d2
Covalent Bonds: Occurs when electron clouds or orbitals overlap
Orbital Hybridization: When s, p, and/or d orbitals (electron clouds) mix to make
a new type of multi-lobed orbital
Hybrid Orbitals:
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•
•
•
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Type
sp
sp2
sp3
dsp3
d2sp3
Hydrid structure
Bond Angles
hybridization of 1 s & 1 p orbital
180o
hybridization of 1 s & 2 p orbitals
120o
hybridization of 1 s & 3 p orbitals
109o
hybridization of 1 d, 1 s & 3 p orbitals
90o & 120o
hybridization of 2 d, 1 s & 3 p orbitals
= 90o
Shape
Linear
Trigonal planer
Tetrahedral
Hexahedral
Octahedral
Electron Cloud Repulsion: In molecules each electron cloud repels other clouds enough
to spread as far apart as possible.
VSEPR: Valence Shell Electron Pair Repulsion
• Clouds of electron pairs repel each other to spread out as much as possible
• There can be fron two to 6 electron clouds
How Bonding Orbitals Correspond between Hybridization & VSEPR within molecules:
Structure
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•
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Hybrid
2 lobes or electron clouds
3 lobes or electron clouds
4 lobes or electron clouds
5 lobes or electron clouds
6 lobes or electron clouds
sp
sp2
sp3
dsp3
d2sp3
VSEPR
Molecular Shape
AX2
AX3
AX4
AX5
AX6
Drill: Calculate the density SO2 at 47oC under 83.1 kPa Pressure:
Lewis Dot Diagrams for each element (Slightly different from EDDs)
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Column I
Column II
Column III
Column IV
Column V
Column VI
Column V
Column V
A single dot
Two single dots
Three single dots
Four single dots
One pair & three single dots
Two pair & two single dots
Three pair & one single dots
Four pair of dots
Drill: Equate each of the following:
sp3
AX2
2 lobes
sp
AX3
4 lobes
3
dsp
AX4
6 lobes
2
sp
AX5
3 lobes
2 3
d sp
AX6
5 lobes
Linear
Trighonal Planer
Tetrahedral
Hexahedral
Octahedral
Drill: Classify the type of bond that forms between the two elements in each below:
Na-Cl
Al-Cl
C-F
H-I
Fe-Cr
P-O
Lewis Dot Diagrams (LDD) of molecules & polyatomic ions:
• Representation of valence electrons and bonds in a molecule or polyatomic ion
Drawing LDDs:
1. Draw the bonding electron dot diagram for each element in the molecule with the element with the most
unpaired e- near the center
2. If there is more than one carbon, connect the carbons by connecting single dots between one carbon &
another
3. Connect a single dot on one atom to a single dot on another (never two on the same atom)(never connect
one dot to more than one other dot)
4. Repeat connecting the dots until all singled dots are connected making sure to obey the octet rule if
possible
5. Recognize polyatomic ions (H2CO3: CO3-2 is a polyatomic ion; thus, the three Os must connect to the C)
6. Redraw the molecule neatly making sure to include all dots
Draw LDDs for:
•
BeCl2
H2O
Drill: Draw the LDD for:
BF3
C2H6
CH4
C4H8
C 4 H8
Drawing LDDs:
• Draw EDDs
• Connect Cs if multiple
• Recognize Polyatomic Ions
• Connect single dots
• Redraw neatly
Draw LDDs for:
C 4 H6
H2C2O4
Coordinate Covalent Bond: A covalent bond in which both electrons are donated by one atom
Draw LDDs for:
SO4-2
Draw LDDs for:
C4H9NO2
Drill: Draw the LDD for:
SO2
HCOOH
C4H8N2O2
H3PO4
Draw LDDs in Groups
Drill: Draw the LDD for:
C4H5NO
Resonance Structures: Equally valid Lewis Dot Diagrams for molecules or polyatomic ions
that have the same shape
NH3
Intermolecular Forces: Weak temporary attractions between atoms from one molecule to another or
another part of a larger molecule (Sometimes called Van der Waals forces)
Types of Intermolecular Forces:
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Hydrogen-bond
• Strongest of the intermolecular forces
• Occurs when H is bound to one highly EN element & connects to another
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Dipole-dipole
• When two polar molecules connect
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Dipole-induced dipole
• When a polar molecule gets near a non-polar one, it induces the non-polar one to become polar;
thus, they connect
•
London dispersion forces
• Instantaneous attraction for fractions of seconds in which non-polar molecules connect
• Very weak force
Draw the LDD for:
PO4-3
P2O7-4
Draw the LDD for:
P3O10-5
C5H8O
Drill: Draw LDDs for:
C 4 H6 O
SCl2
K2SO4
C5H8O
C3H6O2
SiOF2
Test Review:
Identify types of bonds.
Distinguish Periodic Trends (Atomic Radii, Ionization Energies, Electronegativities, etc.)
Identify types of hybridization & VSEPR.
Draw Lewis Dot Diagrams.
Distinguish among intermolecular forces.