Chapter 6 Shapes of Molecules and intermolecular forces

Question 1

what represents a covalent bond in the plane of the paper

Answer 1

a straight line

Question 2

what represents a covalent bond coming towards you

Answer 2

a triangle

Question 3

what represents a covalent bond going away from you

Answer 3

a dashed line

Question 4

why do the covalent bonds go in different directions

Answer 4

to allow the electrons to be as far apart as possible

Question 5

what does the shape of a molecule depend on

Answer 5

the number of outer shell electrons

Question 6

what shape do 2 groups of electrons produce

Answer 6

linear shape

Question 7

what is the angle produced by 2 groups of electrons

Answer 7

180

Question 8

what shape do 3 groups of electrons produce

Answer 8

trigonal planar

Question 9

what is the angle produced by 3 groups of electrons

Answer 9

120

Question 10

what shape do 4 groups of electrons produce

Answer 10

tetrahedral

Question 11

what is the angle produced by 4 groups of electrons

Answer 11

109.5

Question 12

what shape do 5 groups of electrons produce

Answer 12

trigonal bipyramid

Question 13

what is the angle produced by 5 groups of electrons

Answer 13

90 and 120

Question 14

what shape do 6 groups of electrons produce

Answer 14

Octahedral

Question 15

what is the angle produced by 6 groups of electrons

Answer 15

90

Question 16

what do lone pairs do to the shape of a molecule

Answer 16

because they are not bonding they are closer to the nucleus and repel more strongly so for each lone pair the bond angle is decreased by 2.5

Question 17

what is a ‘pure’ covalent bond

Answer 17

covalent bond where electrons are shared equally

Question 18

what two factors affect whether a shared electron pair will be closer to an element

Answer 18

charge of the atom

size of the atom

Question 19

what two qualities will make the shared pair of electrons be closer to the atom

Answer 19

the atom must be bigger and have a greater charge + or -

Question 20

what is a dipole

Answer 20

unequal changes at either end of an atom

Question 21

what is a polar bond

Answer 21

bond that has a permanent dipole

Question 22

what is electronegativity

Answer 22

attraction of the atom for the shared pair of elctrons in a covalent bond

Question 23

what is the general trend for electronegativity in the periodic table

Answer 23

the furhter right the higher the attraction because they have more protons. going down the attraction decreases because the atom is getting larger

Question 24

which element always has the highest electronegativity

Answer 24

Fluorine

Question 25

what happens if the dipoles are equal and symmetrical

Answer 25

the dipoles cancel out

Question 26

what are intermolecular forces

Answer 26

forces between molecules

Question 27

what are intramolecular forces

Answer 27

forces within molecules

Question 28

what does a high electronegtive value mean

Answer 28

strong intermolecular forces and lots of energy is needed to break them

Question 29

what does a low electronegative value mean

Answer 29

weak intermolecular forces and less energy is needed to break them

Question 30

what are the three types of intermolecular bonds (in ascending energy order)

Answer 30

induced dipole - dipole
permanent dipole - dipole
hydrogen bonds

Question 31

what causes an induced/instantaneous dipole - dipole bond

Answer 31

sometimes on random occasion you get more electrons on one side creating an instantaneous dipole which forms a polar molecule

Question 32

summarise the three qualities of an induced/instantaneous dipole - dipole bond

Answer 32

weak
short lived
present in all things

Question 33

what 4 factors can make an induced dipole - dipole bond stronger

Answer 33

more electrons
bigger dipoles
stronger attractive forces
more energy needed to break bonds

Question 34

what is a permanent dipole - dipole bond

Answer 34

a bond where the molecule is always a polar molecule due to electronegativity

Question 35

give the 4 qualities of giant covalent structures

Answer 35

> no intermolecular forces
high melting and boiling point
insoluble in most solvents due to no attraction with polar molecules
dont normally conduct electricity

Question 36

give the 5 qualities of simple molecular structures

Answer 36

>weak intermolecular forces
>strong intramolecular bonds
>low melting and boiling points
>non conductors
>solubility dependent on polarity and type of solvent

Question 37

what does immiscible mean

Answer 37

dont mix

Question 38

what do non polar and polar molecular substances dissolve in

Answer 38

> polar molecular structures dissolve in polar solvents

>non polar molecular structures dissolve in non polar solvents

Question 39

what is a hydrogen bond

Answer 39

special type of strong permanent dipole - dipole intermolecular force

Question 40

what 3 bonds do hydrogen bonds occur in

Answer 40

H - F
H - O
H - N

Question 41

why do hydrogen bonds only occur in three bonds
H - F
H - O
H - N

Answer 41

the three other elements are really electronegatve and quite small

Question 42

what happens during the hydrogen bond

Answer 42

lone pairs of one molecule bond to the exposed proton of the hydrogen in another molecule forming a very strong permanent dipole

Question 43

what three things in a molecule do hydrogen bonds affect

Answer 43

boiling point
viscosity
solubility in water/polar solvent

Question 44

what is viscosity

Answer 44

the stickiness/ lack of fluid in a substance

Question 45

why is H - O the strongest hydrogen bond

Answer 45

it maximises the most out of its potential hydrogen bond energy because it has the same number of lone pairs as bonding pairs