Bonding, Intermolecular Forces

Question 1

define ionic bonding

Answer 1

the electrostatic forces of attraction between oppositely charged ions

Question 2

Why do bonds form?

Answer 2

Because the molecule has a lower energy (i.e. is more stable) than its separated atoms

Question 3

Why do ionic solids have a non-directional bond?

Answer 3

because oppositely charged ions are attracted to each other in all directions

Question 4

define covalent bonding

Answer 4

the electrostatic forces of attractions between the shared pairs of electrons and positively charged nuclei of non-metals

Question 5

define electronegativity

Answer 5

the ability of an atom in a molecule to attract electrons toward itself

Question 6

how does a polar covalent bonds rise?

Answer 6

the difference in electronegativity of the atoms leads to an unsymmetrical electron distribution

Question 7

non polar covalent

Answer 7

• electronically symmetrical
• electronegativity difference = 0-0.4

Question 8

polar covalent

Answer 8

• partial charges
• electronegativity difference<2.0

Question 9

ionic bond

Answer 9

• full charges
• electronegativity difference>2

Question 10

define a lewis structure

Answer 10

a representation of covalently bonded molecules

Question 11

describe VSEPR

Answer 11

Valence Shell Electron Pair Repulsion Model
- observed shapes of molecule arise from each electron group around an atom arranging themselves as far away as possible from other electron groups to minimise repulsions between them

Question 12

electron group

Answer 12

single bond, multiple (double/triple) bond or lone pair

Question 13

five electron group arrangements of minimum energy seen in large majority of molecules

Answer 13

1. linear (2ED)
2. trigonal planar (3ED)
3. tetrahedral (4ED)
4. trigonal bipyramidal (5ED)
5. octahedral (6ED)

Question 14

describe linear molecules (BP only)
- no of bond pairs
- bond angle
- 3 examples
- shape

Answer 14

• 2 bond pairs
• 180
• BeCl2, CO2 and all diatomic molecules
• straight line

Question 15

describe trigonal planar molecules
- no of bond pairs
- bond angle
- 1 example
- shape

Answer 15

• 3 bond pairs
• 120
• BCl3
• flat peace-sign

Question 16

describe tetrahedral molecules
- no of bond pairs
- bond angles
- 1 examples
- shape

Answer 16

• 4 bond pairs
• 109.5
• methane, CH4
• Eiffel Tower

Question 17

describe trigonal bipyramidal molecules
- no of bond pairs
- bond angles
- 1 example
- shape

Answer 17

• 5 bond pairs
• 90 and 120
• PF5
• fidget spinner shot by an arrow

Question 18

describe octahedral molecules
- no of bond pairs
- bond angles
- 1 example
- shape

Answer 18

• 6 bond pairs
• 90
• SF6
• christian cross that has been shot by an arrow

Question 19

why does a lone pair have a greater repulsive effect than a bonding pair?

Answer 19

• lone pair electrons are localised to an atom, so they are closer to each other

Question 20

state the hierarchy of repulsion

Answer 20

lp to lp> lp to bp> bp to bp

Question 21

name the 7 types of lone pair inclusive molecule shapes

Answer 21

• trigonal pyramidal molecules
• v shaped/bent molecules
• square planar molecules
• square pyramidal molecules
• seesaw molecules
• t/arrow shaped molecules
• linear molecules
  (two very silly Swiss singers terrify Lav)

Question 22

describe trigonal pyramidal molecules
- which bpo shape are they like
- no of bp, lp, ed
- bond angles
- example
- shape

Answer 22

• like tetrahedral molecules but without top
• 3 bp, 1 lp, 4 ed
• 107
• NH3
• beheaded Eiffel tower

Question 23

describe v shaped/bent molecules
- which bpo shape are they like
- no of bp, lp, ed
- bond angles
- example

Answer 23

type 1 (SO2 DB):
- like trigonal planar but without top
- 2 bp, 1 lp, 3ed
- 104.5
type 2 (H2O):
- like type 1 but extra pair
- 2 bp, 2 lp, 4 ed
- 104.5

Question 24

describe square planar molecules
- which bpo shape are they like
- no of bp, lp, ed
- bond angles
- example
- shape

Answer 24

• like octahedral but without both vertical bits
• 4 bp, 2 lp, 6 ed
• 90
• XeF4
• cross laid on its side + 2lp above and below

Question 25

describe square pyramidal - which bpo shape are they like - no of bp, lp, ed - bond angles - example - shape

Answer 25

- like octahedral but without bottom vertical bit - 5 bp, 1 lp, 6 ed - 85-87.5 - BrF5 - cross laid on its side + stick up + lp below

Question 26

describe see saw molecules - which bpo shape are they like - no of bp, lp, ed - bond angles - example

Answer 26

- like trigonal bipyramidal but without left side bit - 4 bp, 1 lp, 5 ed - 87.5-90 (equatorial-axial), 117 (e-e) - SF4

Question 27

describe t/arrow shaped molecules - which bpo shape are they like - no of bp, lp, ed - bond angles - example

Answer 27

- like trigonal bipyramidal but only side 3 + 2 lp - 3 bp, 2 lp, 5 ed - 87.5-90 - XeOF2

Question 28

describe linear molecules (WITH lone pairs) - which bpo shape are they like - no of bp, lp, ed - bond angles - example - shape

Answer 28

- like trigonal bipyramidal but only 2 vertical bits - 2 bp, 3 lp, 5 ed - 180 - I3- - straight line

Question 29

dipole moment

Answer 29

a measure of the separation of charge in a molecule arising from the unequal sharing of electrons in polar bonds

Question 30

when a dipole is permanent, the molecule is

Answer 30

polar

Question 31

distinguish between intermolecular and intramolecular forces

Answer 31

intermolecular forces are much weaker than intramolecular forces

Question 32

4 types of intermolecular forces

Answer 32

1. ion-dipole 2. dipole-dipole 3. hydrogen bonds 4. London dispersion forces

Question 33

what are intermolecular forces important in?

Answer 33

state of matter, solubility, boiling point, melting point

Question 34

describe an ion-dipole interaction

Answer 34

- interaction between fully charged ion and partial charges of a polar molecule - the energy of attraction increases with the charge of the ion and decreases with the square of the distance between the ion and dipole

Question 35

describe dipole dipole interactions

Answer 35

polar molecules attract one another when they orient with unlike charges close together

Question 36

describe hydrogen bonding

Answer 36

the dipole-dipole interaction that arises when a hydrogen atom is bonded to Nitrogen, Fluorine or Oxygen atoms with a lone pair of electrons

Question 37

describe dispersion forces

Answer 37

London forces are caused by temporary dipoles which arise in atoms due to uneven distribution of electrons

Question 38

define what it means for an atom's electron cloud to be polarisable

Answer 38

- susceptible to distortion by a neighbouring charge - increases with the number of electrons which increases with molecular mass