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CHM135 > Bonding, Intermolecular Forces > Flashcards

Bonding, Intermolecular Forces Flashcards

1
Q

define ionic bonding

A

the electrostatic forces of attraction between oppositely charged ions

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2
Q

Why do bonds form?

A

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

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3
Q

Why do ionic solids have a non-directional bond?

A

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

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4
Q

define covalent bonding

A

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

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5
Q

define electronegativity

A

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

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6
Q

how does a polar covalent bonds rise?

A

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

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7
Q

non polar covalent

A
  • electronically symmetrical
  • electronegativity difference = 0-0.4
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8
Q

polar covalent

A
  • partial charges
  • electronegativity difference<2.0
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9
Q

ionic bond

A
  • full charges
  • electronegativity difference>2
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10
Q

define a lewis structure

A

a representation of covalently bonded molecules

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11
Q

describe VSEPR

A

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

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12
Q

electron group

A

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

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13
Q

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

A
  1. linear (2ED)
  2. trigonal planar (3ED)
  3. tetrahedral (4ED)
  4. trigonal bipyramidal (5ED)
  5. octahedral (6ED)
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14
Q

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

A
  • 2 bond pairs
  • 180
  • BeCl2, CO2 and all diatomic molecules
  • straight line
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15
Q

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

A
  • 3 bond pairs
  • 120
  • BCl3
  • flat peace-sign
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16
Q

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

A
  • 4 bond pairs
  • 109.5
  • methane, CH4
  • Eiffel Tower
17
Q

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

A
  • 5 bond pairs
  • 90 and 120
  • PF5
  • fidget spinner shot by an arrow
18
Q

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

A
  • 6 bond pairs
  • 90
  • SF6
  • christian cross that has been shot by an arrow
19
Q

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

A
  • lone pair electrons are localised to an atom, so they are closer to each other
20
Q

state the hierarchy of repulsion

A

lp to lp> lp to bp> bp to bp

21
Q

name the 7 types of lone pair inclusive molecule shapes

A
  • 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)
22
Q

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

A
  • like tetrahedral molecules but without top
  • 3 bp, 1 lp, 4 ed
  • 107
  • NH3
  • beheaded Eiffel tower
23
Q

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

A

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

24
Q

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

A
  • like octahedral but without both vertical bits
  • 4 bp, 2 lp, 6 ed
  • 90
  • XeF4
  • cross laid on its side + 2lp above and below
25
Q

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

A
  • 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
26
Q

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

A
  • like trigonal bipyramidal but without left side bit
  • 4 bp, 1 lp, 5 ed
  • 87.5-90 (equatorial-axial), 117 (e-e)
  • SF4
27
Q

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

A
  • like trigonal bipyramidal but only side 3 + 2 lp
  • 3 bp, 2 lp, 5 ed
  • 87.5-90
  • XeOF2
28
Q

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

A
  • like trigonal bipyramidal but only 2 vertical bits
  • 2 bp, 3 lp, 5 ed
  • 180
  • I3-
  • straight line
29
Q

dipole moment

A

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

30
Q

when a dipole is permanent, the molecule is

A

polar

31
Q

distinguish between intermolecular and intramolecular forces

A

intermolecular forces are much weaker than intramolecular forces

32
Q

4 types of intermolecular forces

A
  1. ion-dipole
  2. dipole-dipole
  3. hydrogen bonds
  4. London dispersion forces
33
Q

what are intermolecular forces important in?

A

state of matter, solubility, boiling point, melting point

34
Q

describe an ion-dipole interaction

A
  • 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
35
Q

describe dipole dipole interactions

A

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

36
Q

describe hydrogen bonding

A

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

37
Q

describe dispersion forces

A

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

38
Q

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

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

CHM135 (15 decks)

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