UF CHM2045 Exam 3

Lattice energy

Requires energy to separate (+) and releases energy to form (-)

(g)+(g)-->(s) ; (s)-->(g)+(g)

The 1st EA of an element is

exothermic

Successive EAs are

endothermic

AX5

trigonal bipyramidal ; 90, 120, 180

AX2E2

Bent (water bent) ; 105

AX4E1

See-Saw ; 90, 117, 180

AX3E2

T-Shaped Planar ; 90, 180

AX2E3

Linear ; 180

AX6

Octahedral ; 90, 180

AX5E1

Square Pyramidal ; 90

AX4E2

Square Planar ; 90

Atomic radius / size, metallic character, basicity of oxides

/ increasing down and left

ionization energy

energy required to remove an e- from a neutral, gaseous atom

AX3

Trigonal Planar ; 120

6 electron groups

Octahedral ; 90, 180

AX4

Tetrahedral ; 109.5

AX3E1

Trigonal Pyramidal ; 107

Molecular and electron geometry are =

when the molecule has 0 lone pairs

Isoelectronic

same electron configuration and number of ions

Properties of metals

1) lustrous

2) solid at room temp

3) good electrical conductors

4) good head conductors

5) malleable

6) ductile

7) LOSE ELECTRONS

5 electron groups

Trigonal Bipyramidal ; 90, 120, 180

4 electron groups

Tetrahedral ; 109.5

AX2E1

Bent (v-shaped) ; 117

3 electron groups

Trigonal Planar ; 120

Electronegativity, electron affinity, acidity of oxides, nonmetallic character, ionization energy,

/ increasing right and up

Strongest & shortest bond

Triple bond

Molecular geometry is asking for

shape

2 electron groups

Linear ; 180

Exceptions to ionization energy trend

N>O

Be>B

P>S

Mg>Al

AX2

Linear ; 180

Exception to atomic radius trend

Ga is smaller than Al

In isoelectronic ions, the ion with the ______ # of protons will be the smallest

highest

How to solve for Lattice Energy (bigger radius = smaller LE)

|charge x charge|

Higher Lattice Energy = _____ melting point

higher

Single bonds are the ____ and _____

weakest, longest

Short bonds, small atoms

high bond energy/strength

Long bonds, large atoms

low bond energy/strength

H, P, and Te's electronegativity

2.1

EN of noble gases

0

EN of I, C, and S

2.5

EN of At

2.2

EN of Cl and N

3.0

EN of As

2.0

EN of B

1.5

EN of O

3.5

EN of F

4.0

EN of Si

1.8

EN of Se

2.4

EN of Br

2.8

a single bond is referred to as a

sigma bond

in MO theory, mixing 2 s orbitals creates

sigma (o looking symbol) and anti bond (o*)

in MO theory, mixing 2 p orbitals creates

sigma (o), pi, anti sig and anti pi

bond order equal to zero indicates

that the molecule is less stable than the individual atoms that make it up and is unlikely to exist/form

higher bond order =

stronger bond

bond order greater than 0

indicates that the molecule is more stable than the individual atoms that make it up and is likely to exist

equation for bond order using MO theory:

BO=1/2(#electrons in bonding - #electrons in anti-bond)

the anti-bond molecular orbital is ____ in energy than the original

higher

what happens when electrons are out-of-phase?

the overlap weakens the attraction and forms an anti-bonding molecular orbital

what happens when electrons are in-phase?

the overlap reinforces the attractions and creates a bonding molecular orbital

3 properties of a molecule described by MO theory:

spectral, resonance, magnetic

VSEPR theory and valence bond theory are useful in determining ______ and ______

shape and hybridization

when two different orbitals mix, the result is a

hybrid orbital

hybridization of a central atom is determined by

counting the number of electron groups

according to Valence Bond Theory, what is counted as areas of high electron density?

single bonds, double bonds, triple bonds, lone pairs, radicals

degenerate

equal energies

equatorial

in the plane of the paper

a triple bond has

1 sigma bond and 2 pi bonds

a double bond has

one sigma bond and one pi bond

is a sigma bond stronger or weaker than a pi bond?

stronger

how is a pi bond formed?

by the "above and below" or "side-by-side" overlap of two unhybridized p orbitals

a double bond contains how many pi bonds /// triple bond?

double bond = 1pi ; triple bond = 2pi

a sigma bond ____ the overall energy of an element

lowers

a sigma bond _____ the electron density around the central atom

delocalizes

how is a sigma bond formed?

by the "end to end" overlap of two atomic orbitals or two hybrid orbitals or one hybrid orbital with an atomic orbital

fundamentals of MO theory

1) the combination of 2 atomic orbitals creates 2 molecular orbitals

2) an electron within an atomic orbital moves like a wave

3) when 2 electrons overlap, they are either in sync or not in sync