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bonding 2 Flashcards

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1
Q

what is ionic bonding

A

electrostatic force of attraction between oppositely charged ions formed by electron transfer

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2
Q

what are electrostatic forces of attraction in an ionic lattice

A

ions in lattice are attracted to every other oppositely charged ion

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3
Q

physical properties of ionic compounds

A
  1. high melting and boiling point - due to large amount of energy to overcome strong electrostatic forces of attraction
  2. soluble in polar solvents - soluble substance e.g water, surrounds the ions and overcome electrostatic forces between the ions
    (if charge of ions increase, solubility decreases as water cannot overcome the electrostatic forces of attraction)

3.do NOT conduct electricity when solid - ions locked in place by electrostatic forces of attraction and cant carry a charge
dissolved in water + conducts electricity as they’re free to move

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4
Q

what molecule has bond angle 180

A

linear
e.g beryllium chloride
Cl – Be – Cl

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5
Q

which molecule has bond angle 104.5

A

v - shaped or non linear
e.g H2O

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6
Q

which molecule has bond angle 120

A

trigonal planar
e.g BF3

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7
Q

which molecule has bond angle 107

A

triangular pyramid
e.g NH3

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8
Q

which molecule has bond angle 109.5

A

tetrahedral
e.g CH4 methane / NH3 ammonium

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9
Q

which molecule has bond angle 90 AND 120

A

trigonal bipyramid
e.g PCl5

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10
Q

which molecule has bond angle 90

A

octahedral
e.g SF6

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11
Q

for every lone pair present, what happens to the bond angle between covalent bonds

A

reduced by 2.5 degrees

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12
Q

how are dative bonds presented

A

indicated using an arrow from lone electron pair
H
|
H —- N ➜ H
|
H

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13
Q

why do lone pairs reduce bond angle by 2.5 degrees

A

repel more strongly than bonding pairs

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14
Q

define electronegativity

A

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

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15
Q

what happens to electronegativity ALONG a PERIOD

A

increases

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16
Q

what does the power of electronegativity depend on

A
  1. size of positive charge on nucleus
    (more protons = increased positive charge ➜ increases attraction between nucleus and pair of electrons in covalent bond
  2. atomic radius
    (smaller atomic radius = closer bonding electrons to nucleus )
    L➜R (periodic table) atomic radius decreases
  3. shielding of nucleus of nucleus by electrons in inner shells
    (more inner shells + lower electronegativity)
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17
Q

whats a dipole

A

a separation of charge

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18
Q

whats a pure covalent bond

A

has no dipole

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19
Q

what does delta δ show

A

shows that the charge is small
as the electron pair has shifted towards the MORE electronegative atom

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20
Q

where does the delta negative δ- go

A

goes on more electronegative element

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21
Q

name the 3 intermolecular forces

A
  1. van de waals forces (induced dipole)
  2. permanent dipole
  3. hydrogen bonding
22
Q

whats a polar bond

A

bonding of two atoms with different electronegativites

23
Q

what are simple molecular substances

A

substances with small molecules
each molecule has fixed number of atoms

24
Q

where do intermolecular forces take place

A

in-between molecules

25
Q

intermolecular forces properties

A

weaker than covalent bonds
easily broken by high temp

26
Q

what happens when intermolecular forces are heated

A

molecules move faster

intermolecular forces break at a certain temp

causes molecules to move away from each other

27
Q

why do intermolecular forces have low boiling point

A

small amount of energy to break intermolecular forces

28
Q

what are induced dipole-dipole interactions (van de waals)

A
  • weakest type of intermolecular force
  • caused by random electron movement
  • acts as an induced dipole between molecules
29
Q

what does strength of van de waals depend on

A

depends on number of electrons
(larger amount of electrons = higher boiling point - experience stronger van de waals)

30
Q

what are permanent dipole-dipole interactions

A

when permanent dipoles leads to attraction
acts between polar molecules
δ+ and δ- attract each other
hold molecules together in lattice-like structure

31
Q

what is the strongest type of intermolecular force

A

hydrogen bonding

32
Q

what is the weakest type of intermolecular force

A

van de waals

33
Q

where do hydrogen bonds only form between

A

between 3 most electronegative atoms:
nitrogen
oxygen
fluorine

(all have at least one lone pair of electrons)

34
Q

what two conditions are needed for hydrogen bonding to take place

A
  1. hydrogen atom bonded to strong electronegative element
  2. electronegative atom must have at least one lone pair of electrons
35
Q

what is hydrogen bonding

A

type of permanent dipole dipole bond
strongest intermolecular forces between neutral molecules
act between molecules containing permanent dipoles

36
Q

why does water have a high melting and boiling point

A

it takes a great deal of energy to break the hydrogen bonds

37
Q

properties of after due to hydrogen bonding

A

ice is less dense of liquid form therefore ice floats on water
liquid water = water molecules moving randomly freezing point = water molecules in ordered structure = ice - stabilised by hydrogen bonds
(in ice - water molecules are further apart than in liquid water making it less dense & floats)

38
Q

what bond is between atoms of simple molecular substances

A

covalent

39
Q

what do simple molecular substances have

A

small molecules with fixed number of atoms

40
Q

2 examples of giant covalent structures

A

diamond and graphite

41
Q

properties of simple molecular substances

A

low melting and boiling points due to weak intermolecular forces

42
Q

what happens when you cool a simple molecular substance below its melting point

A

becomes a solid simple molecular lattice

43
Q

molecule of iodine

A

consists of two iodine atoms joined by a single covalent bond with intermolecular forces between the molecules

44
Q

what are non-polar molecules

A

atoms that have same electronegativity
means that only van de waals can act between the molecules

45
Q

what the solubility of simple molecular substance depend on

A

depends on whether the substance is polar or none polar

46
Q

iodine solubility

A

solid at room temp
iodine molecules held in simple molecular lattice by van de waals

47
Q

what happens when non polar substances e.g iodine dissolve in non polar substances

A

solvent molecules form van de waals to iodine molecules

48
Q

why are non polar substances insoluble in polar e.g water solvents

A

molecules with hydrogen bond remain hydrogen bonded rather than forming van de waals with non polar molecules

49
Q

general rule of polar substances

A

polar substances dissolve in polar solvents

50
Q

where does hydrogen bonding take place

A

in compounds that have a hydrogen atom attached to one of the three most
electronegative atoms

chemistry (6 decks)

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