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THINGS TO REVIEW: -Dot Diagrams -Shape -Bond Angles -Polarity -Counting sigma bonds
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What is Ionic Bonding
The transfer of electrons
What is a lattice and what is lattice energy?
Lattice = stable, ordered, solid 3D array of ions
Lattice Energy = The energy required to completely separate a mole of a solid ionic compound into gaseous ions
Use Coulombs law to justify lattice energy
Greater charge = greater charge (increases across)
Greater distance = weaker attraction (decreases down)
always look at charge first (greater the charge greater the lattice energy)
Characteristics of Ionic Solids (6 characteristics)
Hard
Brittle
High Melting Points
Transition Metals loses e-
Mostly soluble in water
Does NOT conduct as a solid
What is a amorphous solid?
A solid where the arrangement lacks any pattern
ex) glass, wax, and sand
Ionic Solids (3 Parts: Formula, Structure/Bonding, Properties
Recognizing a Formula
Compounds of metal cations + nonmetal anions. ex) NaCl FeS
Structure & Bonding
3D locked in place by strong ionic bonds
Properties
Brittle
High Melting
Non-conductors in water
Metallic Solid
Recognizing a Formula
Metal atoms ONLY
Structure & Bonding
3D metal ions surrounded by delocalized e- (do not belong to any atom/they move freely about the network)
Properties
Good conductors of heat & electricity
Malleable
Ductile
Alloys
Covalent-network solids
Recognizing a Formula
Carbon (graphite & diamond); metalloids: Si, Ge; and compounds of metalloids (SiC, BN)
Structure & Bonding
An extended network of covalent bonds
Properties
Hard
High-Melting
Insoluble in water
Doesn´t conduct heat or electricity
Molecular solids
Recognizing a Formula
Compounds of nonmetals ONLY
Structure & Bonding
Individual contently bonded molecules held together by weak inter molecular forces
Properties
Soft
Low-Melting
Nonconductors
How do metallic bonds form?
Outer energy levels overlap
Subsitutional Alloys
A homogeneous alloy in which different atoms of similar size occupy sites in the lattice
Interstitial Alloys
Where smaller atoms (usually nonmetals) fit into spaces between larger atoms (usually a metal)
Covalent Bonding
Sharing of e-
Low-Melting
Don´t dissolve easily in water
Doesn´t conduct electricity in solutions
Electronegativity Difference and how that determines the type on bonds
0-0.4 = Nonpolar covalent
0.4-2.0 = Polar covalent
> 2.0 = Ionic
Polar Covalent Bond
unequal sharing of electrons
dipole moment
A dipole moment is a measurement of the separation of two opposite electrical charges (magnitude x distance = charge)
A measurement of 2 electrical charges creates a dipole moment
Nonpolar Covalent Bond & Shapes that are ALWAYS Nonpolar
equal sharing of electrons
Linear
Trigonal Planar
Tetrahedral
Square Planar
Octahedral
Trigonal Bipyramidal
Exceptions to Lewis Dot Structures
H only needs 2 e-
Groups 1, 2, 13 need twice their # of e-
O & F can’t be the central atom
What is resonance
Multiple ways of drawing the same structure
How to determine the best structure
Count e- in line pairs and ½ e- it shares for each atom
Subtract from the # of e- for that atom
Best structure = one with the fewest charge
Puts a negative charge on the most EN atom
What does VESPER theory describe?
The repulsion between electron pairs causes molecular shapes to adjust so that the valence-electron pairs stay as far away as possible.
VESPER Theory : Nonbonding/Lone Pairs
Subtract 2 for every lone pair from the original angle
repulsion →smaller angle
VESPER Theory: Multiple(triple or double) Bonds affect bond angles
Place greater e- density on 1 side of the central atom than do single bonds
expands angle → >120 degrees
How to analyze larger molecules (refer back to page 8 of note packet)
Look at 1 particle atom instead of the molecule as a whole
Split it
Sigma Bond
head-head overlap: cylindrical
symmetry of e- density about the inter-nuclear axis
ALL SINGLE BONDS
STRONGER than pi bonds
SINGLE BOND = 1 SIGMA (the 6 looking symbol)
Pi Bonds
side-side overlap
e- density below inter-nuclear axis
founding double and triple bonds
Delocalized pi bonding
resonance
double/triple bonds
Double Bond —> 1 6 + 1π
Triple Bond —> 1 6 + 2π
How to read inter-nuclear distance graphs
bond length = distance between atoms goes across
bond energy does up & down
the greater the charge the stronger the bond energy and the shorter the bond length
Linear
Bonded: 2
Lone: 0
Angle: 180
Trigonal Planar
Bonded: 3
Lone: 0
Angle: 120
Tetrahedral
Bonded: 4
Lone: 0
Angle: 109.5
Trigonal Bipyramidal
Bonded: 5
Lone: 0
Angle: 90 & 120
Octahedral
Bonded: 6
Lone: 0
Angle: 90