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Chemistry > Shapes Of Molecules And IMF > Flashcards

Shapes Of Molecules And IMF Flashcards

1
Q

What is a valence shell?

A

The outer shell

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2
Q

What are lone electron pairs?

A

Two electrons that are not involved in a Bond

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3
Q

What is the valence shell electron pair repulsion theory?

A

Pairs of electrons in valence shell repel each other as far as possible

Multiple bonds have same effect as single bonds

Lone pair of electrons have larger repelling effect than bonded electrons (more lone electrons= reduces bond angle)

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4
Q

How do you determine the shape of a molecule and bond angles?

A

Draw dot and cross diagram

Take into account repelling effects of bonds

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5
Q

What is the shape and bond angle of a molecule with 2 bonded pair of electrons/ regions?

A

Linear

180

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6
Q

What is the shape and bond angle of a molecule with 3 bonded pair of electrons/ regions?

A

Trigonal planar

120

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7
Q

What is the shape and bond angle of a molecule with 4 bonded pair of electrons/ regions?

A

Tetrahedral

109.5

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8
Q

What is the shape and bond angle of a molecule with 6 bonded pair of electrons/ regions?

A

Octahedral

90

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9
Q

What is a dative bond?

A

A covalent bond where nth electrons come from the same atom

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10
Q

What does the triangle in a dot and cross diagram signify?

+ when is it used?

A

Used in poly atomic ions

To signify electrons gained

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11
Q

What is a covalent bond?

A

The attraction between the positive nucleus of two atoms and the negative electrons they share .

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12
Q

What is electronegetivity?

A

The ability of an atom to attract the bonded pair of electrons in a covalent

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13
Q

What are the electronegativity values called?

A

Pauling electronegativity values

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14
Q

What is the most electronegative atom?

A

Fluorine

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15
Q

What is a polar bond ?

A

A covalent bond where each atom has different electronegativities with + and - partially charges on the atoms

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16
Q

Will the more electronegative atom has a + or - partial charge?

A

Partial negative charge

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17
Q

What is a dipole?

A

The separation (short distance) of partial charges in a molecule

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18
Q

What is a permanent dipole?

A

The separation of partial charges across a polar bond due to different electronegativities

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19
Q

When is molecule polar?

A

When a molecule has more than one polar bond and is not symmetrical

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20
Q

Why are some molecules non-polar even though they have 2+ polar bonds?

A

The molecule is symmetrical so the dipole acts in opposite directions and cancels out

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21
Q

What are intermolecular forces?

A

Weak attraction between molecules

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22
Q

What are the types of intermolecular forces?

A

Induced dipole-dipole attraction (London forces)

Permanent dipole-dipole interactions

Hydrogen bonding

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23
Q

What are temporary dipoles and why do they form?

A

Dipoles caused by uneven distribution of electrons

Form due to random nature of electron movement

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24
Q

What is an induced dipole and how is it created?

A

A dipole caused by the presence of a temporary dipole in a molecule

Chain reaction

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25
What is a London force?
The force of attraction between induced dipoles
26
Where do London forces occur?
In all molecules
27
What does the head of an arrow indicate in terms of dipoles?
Partial negative charge
28
What causes a stronger London force ?
More electrons
29
Why do elements with more electrons have higher MP and BP?
More electrons= stronger London forces (occurs in all molecules and is a type of intermolecular force) More energy needed to break the bonds
30
What is a permanent dipole-dipole interaction?
Type of intermolecular force. Between two polar molecules with permanent dipoles Attraction is between + and - partial charges
31
What occurs to permanent dipole-dipole interactions in a liquid?
They are constantly breaking and reforming (molecules move)
32
What occurs to permanent dipole-dipole interactions in a solid?
The interactions are constant so hold molecules in a fixed position
33
What is a hydrogen bond also known as?
Very strong permanent dipole-dipole interaction
34
What is a hydrogen bond?
Attraction between hydrogen atom bonded to electronegative atom in one molecule + Lone pair of electrons of an electronegative element in a different molecule
35
Give examples of molecules with hydrogen bonding
H2O NH3 HF
36
Why is ice less dense than water?
Water molecules are held in open lattice structure in ice (very regular structure) making it less dense. When it melts the lattice collapses
37
How are molecules in a simple molecular lattice held in place?
By weak intermolecular forces
38
Are the MP and BP of simple molecular lattices high or low ? Why?
Low Weak intermolecular forces are easy to overcome
39
Why are simple molecular lattices poor conductors of electricity?
They aren’t charged
40
Are highly polar molecules soluble or insoluble in water? Why?
Soluble They can interact with the dipoles in water
41
What are simple molecules soluble and insoluble in? Why?
Soluble = non-polar substances Insoluble= water Due to weak dipoles
42
What is an instantaneous dipole?
A dipole only present for an instant (caused by the accumulation of electrons)
43
What is the name for the electrons involved in a covalent bond?
Bonding pair
44
What is the rule for drawing ions?
Same as uncharged molecules (based on types and number of bonding regions)
45
What effects electronegativity?
Electron shielding Nuclear charge Atomic radius
46
How does electronic shielding affect electronegativity?
More shells= less electronegative Inner shell electrons repel outer shell electrons making attraction to nucleus weaker
47
What letter is used to depict a partial charge?
Lower case delta
48
What value determines a covalent, polar covalent and ionic bond?
Covalent = 0 Polar covalent = 0 >_ 0.18 Ionic = > 1.8
49
In a simple molecular lattice what forces hold the molecules in place?
London forces
50
What may occur due to permanent dipole-dipole interaction?
The partial charges may increase Electrons are reopened by partial charge on neighbouring molecule making them move further away from partial positive charge
51
How many hydrogen bonds are there per water molecule in ice?
4
52
What are van der Waals forces?
Induced dipole-dipole interactions (London forces) And Permanent dipole-dipole interactions
53
What does a lone pair reduce the bond angle by?
2.5 per lone pair
54
What increases the strength of London forces ?
More electrons Larger SA = bigger exposed electron cloud = greater attraction
55
What are the anomalous properties of water?
Higher M+Bp than expected Ice is less dense than water
56
Explain why ice is less dense than water
There are more hydrogen bonds in ice than water (4) When ice melts some hydrogen bonds break and molecules are closer so it’s more dense Hydrogen bonds are relatively long and so hold water molecules in an open lattice structure
57
Place the IMF in order of increasing strength
Induced dipole-dipole Permanent dipole-dipole Hydrogen
58
What is the structure of simple molecules held by London forces
Molecular lattice
59
How many bonded and lone pairs does trigonal pyramidal have? What is the bond angle?
Bonded= 3 Lone= 1 Angle =107
60
How many bonded and lone pairs does a molecule with bond angle 104.5 have? What is it’s name?
2 bonding regions (double bonds) Two lone. Non-linear
61
What shape of molecule has two bond angles and what are they?
Trigonal bipyramidal 90+ 120
62
Are molecules with hydrogen bonding soluble in water? | Why?
Yes Can form hydrogen bonds with water
63
Describe the solubility of polar and non-polar solutes
Like dissolves like
64
Will a polar solvent dissolve and non-polar solute? Why?
No Partial charges aren’t strong enough the separate atoms (break covalent bond)
65
Give pauling En values for pure covalent, polar covalent and ionic bonds
``` Pure = 0 Polar= up to 1.8 Ionic= 1.8+ ```
66
Define bond in molecules with 0, 0.6 and 2.5 difference in electronegetivity values of atoms
0= pure covalent 0. 6 =polar covalent 2. 5 =ionic
67
What IMF does water have?
London forces Permanent dipole-dipole Hydrogen
68
Why does Br2 have a higher boiling point than f2?
Br has more electrons so stronger London forces

Chemistry (28 decks)

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