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bonding 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 do square brackets tell us
[Na]+

A

charge is spread over whole ion

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3
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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4
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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5
Q

ionic compounds examples

A

sodium chloride NaCl

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6
Q

what is covalent bonding

A

between two non-metals
electrons are shared between two outer shells to achieve a full outer shell (same electron configuration of a noble gas)

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7
Q

what are the pair of electrons attracted to in covalent bonding

A

the two nuclei of atoms forming the bond

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8
Q

what does the line represent in covalent bonds
H—–H

A

shared pair of electrons

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9
Q

what is dative covalent bonding/ coordinate bonding

A

when at atom uses a lone pair of electrons to form a covalent bond
(both electrons in shared pair are supplied from a single atom)

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10
Q

what is a lone pair

A

electrons that are not shared with another atom

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11
Q

for a dative bond to form, what must the acceptor atom be

A

electron deficient (available orbitals for electrons to occupy)

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12
Q

what is average bond enthalpy

A

tells us the strength of the bond

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13
Q

what do the solid lines tell us on shapes of molecule

A

that two bonds and atoms attached lie on the plane of the screen/page

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14
Q

what does a solid wedge tell us on shapes of molecule

A

bond is coming out of plane of page

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15
Q

what do the dotted wedge tell us on shape of molecules

A

bond is projected back behind plane of page

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16
Q

what is electron pair repulsion theory

A

shape of molecule is determined by the electron pairs surrounding the central atom (referring to outer shell)
electrons repel all of other electron pairs
electrons move as far apart as possible to minimise repulsion

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17
Q

what molecule has bond angle 180

A

linear
e.g beryllium chloride
Cl – Be – Cl

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18
Q

which molecule has bond angle 104.5

A

v - shaped or non linear
e.g H2O

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19
Q

which molecule has bond angle 120

A

trigonal planar
e.g BF3

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20
Q

which molecule has bond angle 107

A

triangular pyramid
e.g NH3

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21
Q

which molecule has bond angle 109.5

A

tetrahedral
e.g CH4 methane / NH3 ammonium

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22
Q

which molecule has bond angle 90 AND 120

A

trigonal bipyramid
e.g PCl5

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23
Q

which molecule has bond angle 90

A

octahedral
e.g SF6

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24
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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25
Q

how are dative bonds presented

A

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

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26
Q

why do lone pairs reduce bond angle by 2.5 degrees

A

repel more strongly than bonding pairs

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27
Q

define electronegativity

A

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

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28
Q

what happens to electronegativity ALONG a PERIOD

A

increases

29
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)
30
Q

what happens to electronegativity DOWN a GROUP

A

decreases

31
Q

what are some of most electronegative elements

A

fluorine
oxygen
nitrogen
chlorine

32
Q

whats a dipole

A

a separation of charge

33
Q

are elements on right or left of periodic table more electronegative

A

right

34
Q

whats a pure covalent bond

A

has no dipole

35
Q

how to show that a bond is polar

A

write delta positive (δ+) and delta negative (δ-)
to show charges

36
Q

what does delta δ show

A

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

37
Q

where does the delta negative δ- go

A

goes on more electronegative element

38
Q

name the 3 intermolecular forces

A
  1. van de waals forces (induced dipole)
  2. permanent dipole
  3. hydrogen bonding
39
Q

whats a polar bond

A

bonding of two atoms with different electronegativites

40
Q

what are simple molecular substances

A

substances with small molecules
each molecule has fixed number of atoms

41
Q

where do intermolecular forces take place

A

in-between molecules

42
Q

intermolecular forces properties

A

weaker than covalent bonds
easily broken by high temp

43
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

44
Q

why do intermolecular forces have low boiling point

A

small amount of energy to break intermolecular forces

45
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
46
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)

47
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

48
Q

what is the strongest type of intermolecular force

A

hydrogen bonding

49
Q

what is the weakest type of intermolecular force

A

van de waals

50
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)

51
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
52
Q

what is hydrogen bonding

A

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

53
Q

where does hydrogen bonding take place

A

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

54
Q

why does water have a high melting and boiling point

A

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

55
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)

56
Q

what bond is between atoms of simple molecular substances

A

covalent

57
Q

what do simple molecular substances have

A

small molecules with fixed number of atoms

58
Q

2 examples of giant covalent structures

A

diamond and graphite

59
Q

properties of simple molecular substances

A

low melting and boiling points due to weak intermolecular forces

60
Q

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

A

becomes a solid simple molecular lattice

61
Q

molecule of iodine

A

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

62
Q

what are non-polar molecules

A

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

63
Q

what the solubility of simple molecular substance depend on

A

depends on whether the substance is polar or none polar

64
Q

iodine solubility

A

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

65
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

66
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

67
Q

general rule of polar substances

A

polar substances dissolve in polar solvents

68
Q

what dont simple molecular substances contain

A

mobile charged particles
(means that simple molecular substances cant conduct electricity)

chemistry (6 decks)

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