Shapes and IMFs

Question 1

what is the shape of a molecule determined by?

Answer 1

the number of bonding pairs and lone pairs in the outer shell of the central atom

Question 2

what is the theory for shape of molecules?

Answer 2

electron pairs repel as far apart as possible, and lone pairs repel more than bonded pairs

Question 3

what is the shape and bond angle of beryllium chlorine?

Answer 3

2 bonding pairs, no lone pairs
shape= linear
bond angle= 180

Question 4

what is the shape and bond angle of boron fluoride?

Answer 4

3 bonding pairs, no lone pairs
shape= trigonal planar
bond angle= 120

Question 5

what is the shape and bond angle of methane?

Answer 5

4 bonding pairs, no lone pairs
shape= tetrahedral
bond angle= 109.5

Question 6

what is the shape and bond angle of sulfur hexafluoride?

Answer 6

6 bonding pairs, no lone pairs
shape= octahedral
bond angle= 90

Question 7

what is the shape and bond angle of ammonia?

Answer 7

3 bonding pairs, 1 lone pairs
shape= pyramidal
bond angle= 107

Question 8

what is the shape and bond angle of water?

Answer 8

2 bonding pairs, 2 lone pairs
shape= non-linear
bond angle= 104.5

Question 9

what are bonding pairs called if they are double and triple bonds?

Answer 9

bonding regions

Question 10

what are the 3 intermolecular forces?

Answer 10

permanent dipole-dipole
induced dipole-dipole
hydrogen bonds

Question 11

what are permanent dipole-dipole forces/

Answer 11

a weak attractive forces between neighbouring permanent dipoles- polar molecules always have them

Question 12

what are induced dipole-dipole forces?

Answer 12

1) electrons have a random movement in a molecule
2) this creates an instantaneous dipole
3) this induces dipoles in neighbouring molecules
they are the weakest forces, and all molecules have them

Question 13

which factors affect the strength of IDDs?

Answer 13

the greater the number of electrons, the stronger the force, the higher the boiling point

Question 14

how would the boiling point of halogens change down the group?

Answer 14

1) the number of electrons increases down the group
2) therefore there are stronger induced dipole-dipole forces
3) therefore, more energy is required

Question 15

what is hydrogen bonding?

Answer 15

the strongest IMF- between the hydrogen atom of one molecule and the lone pair of electrons on a highly electromagnetic atom on a different molecule
ONLY between H-O, H-N, H-F

Question 16

draw hydrogen bonding between 2 water molecules

Answer 16

need dipoles, lone pair of electrons and label of H-bond

Question 17

how does H-bonding explain the 2 anomalous properties of water?

Answer 17

1) relatively high boiling point because the stronger hydrogen bonds require more energy to be broken
2) ice is less dense than water because water molecules are held further apart by H-bonds in a lattice

Question 18

what is electronegativity?

Answer 18

the ability an atom has to attract a bonding pair of electrons in a covalent bond

Question 19

which factors affect electronegativity?

Answer 19

1) the number of protons in the nucleus
2) the distance of the shared pair of electrons from the nucleus
3) the shielding effect of full shells of electrons between the outer electrons and the nucleus.

Question 20

what happens to electronegativity across a period?

Answer 20

it increases

Question 21

what happens to electronegativity down a group?

Answer 21

it decreases

Question 22

what is the most electronegative element and what is its electronegativity?

Answer 22

fluorine = 4.0

Question 23

describe the bond polarity of H-H

Answer 23

the atoms are identical
electronegativities are equal
the electron pair is shared equally ie electron density is evenly distributed
the bond is non-polar

Question 24

describe the bond polarity of H-Cl

Answer 24

the atoms are different
chlorine is more electronegative than hydrogen
the electron pair lies closer to chlorine
the bond is polar as shown by the delta negative and positive

Question 25

what is meant by permanent dipole?

Answer 25

a difference in electronegativities leading to one atom being slightly negative and one being slightly positive

Question 26

is carbon dioxide a polar molecule?

Answer 26

each C=O has a permanent dipole because the oxygen is more electronegative than carbon.
the dipoles cancel as the molecule is symmetrical
it is non-polar