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chemistry 2 > bonding p1,2 > Flashcards

bonding p1,2 Flashcards

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1
Q

what are ions?

A

charged particles that are formed when an atom loses or gains electrons

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2
Q

what is the charge of an ion when electrons are gained?

A

negative
positive when lost

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3
Q

what are molecular ions?

A

covalently bonded atoms that lose or gain electrons

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4
Q

which electrons are lost when as atom becomes a positive ion?

A

electrons in the highest energy levels

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5
Q

do metals usually gain or lose electrons?

A

lose electrons

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6
Q

which are the 4 elements that don’t tend to form ions and why?

A

Beryllium, boron, carbon and silicon
requires lots of energy to transfer outer shell electrons

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7
Q

what are the 3 main types of chemical bonds?

A

ionic, covalent, metallic

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8
Q

ionic bonding

A

electrostatic attraction between positive nucleus and negative ions

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9
Q

what determines the strength of an ionic bond?

A
  • ionic radius
  • ionic charge
  • ionic bonding is stronger and the melting points higher when the ions are smaller and have higher charges
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10
Q

what is the trend in ionic radius down a group?

A

increases down the group
because the ions have more shells of electrons and thus the outermost electron experiences less pull from positive nucleus

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11
Q

what are the physical properties of ionic compounds?

A
  • high melting points
  • non conductor of electricity when solid
  • conductor when in solution or molten
  • brittle
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12
Q

in a solution of CuCrO4 with connected electrodes which electrode will the 2 ions (Cu2+ & CrO2-) migrate to?

A

Cu2+ - migrates to negative electrode
CrO2- - migrates to positive electrode

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13
Q

covalent bonding

A

electrostatic attraction between a shared pair of electrons and the nuclei

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14
Q

metallic bonding

A

electrostatic attraction between the positive metal ions and the sea of delocalised electrons

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15
Q

why do giant ionic lattices conduct electricity when liquid but not when solid?

A

in solid state the ions are in fixed positions and thus cannot move
when in liquid state the ions are mobile and thus can freely carry charge

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16
Q

giant ionic lattices have high melting and boiling point. why?

A

large amount of energy is required to overcome the electrostatic bonds

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17
Q

what type of solvents do ionic lattices dissolve in?

A

polar solvents
e.g. water

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18
Q

why are ionic compounds soluble in water?

A

water has a polar bond
hydrogen atoms have a 1+ charge and oxygen atoms have a 2- charge
these charges are able to attract charged ions

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19
Q

what is it called when atoms are bonded by a single pair of shared electrons?

A

single bond

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20
Q

what is the effect of multiple covalent bonds on bond length and strength?

A

double/triple bonds exert greater electron density therefore the attraction between nucleus and electron is greater resulting in a shorter and stronger bond

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21
Q

what is a lone pair?

A

electrons in the outer shell that are not involved in the bonding

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22
Q

what is formed when atoms share two pairs of electrons?

A

double bond

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23
Q

what is a dative covalent bond?

A

a bond where both of the shared electrons are supplied by one atom

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24
Q

how are oxonium ions formed?

A

formed when acid is added to water
H3O+

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25
Q

what does expansion of the octet mean?

A

when a bonded atom has more than 8 electrons in the outer shell

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26
Q

what are the types of covalent structure?

A
  • single molecular lattice
  • giant covalent lattice
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27
Q

describe the bonding in simple molecular structures

A

atoms within the same molecule are held by strong covalent bonds and different molecules are held by weak intermolecular forces

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28
Q

why do simple molecular structures have low melting and boiling points?

A

small amount of energy is enough to overcome the intermolecular force

29
Q

can simple molecular structures conduct electricity?

A

no - no free charged particles to move around

30
Q

simple molecular structures dissolve in what type of solvent?

A

non polar solvents

31
Q

examples of giant covalent structures

A

diamond, graphite, silicon dioxide

32
Q

properties of giant covalent structures?

A
  • high melting and boiling point
  • non conductors (except graphite)
  • insoluble in polar and non polar solvents
33
Q

how does graphite conduct electricity?

A

delocalised electrons present between the layers are able to move freely carrying the charge

34
Q

why do giant covalent structures have high melting and boiling points?

A

strong covalent bonds within the molecules need to be broken which requires lots of energy

35
Q

describe the structure of diamond

A

3D tetrahedral structure of C atoms, with each C atom bonded to 4 others

36
Q

what does the shape of a molecule depend on?

A

number of electron pairs in outer shell, number of electrons which are bonded/lone pairs

37
Q

2 bonded pairs shape

A

linear
180*

38
Q

3 bonding pairs shape

A

trigonal planar
120*

39
Q

4 bonded pairs shape

A

tetrahedral
109.5*

40
Q

5 bonded pairs shape

A

trigonal bipyramid
90* and 120*

41
Q

6 bonded pairs

A

octahedral
90*

42
Q

3 bonded pairs 1 lone pair shape

A

pyramidal
107*

43
Q

2 boned pairs and 2 lone pairs shape

A

non linear (bent)
104.5*

44
Q

by how many degrees does each lone pair reduce the bond angle?

A

2.5*

45
Q

electronegativity

A

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

46
Q

what scale is electronegativity measured on?

A

Pauling scale

47
Q

which direction of the periodic table does electronegativity increase?

A

top right, towards fluorine

48
Q

what does is mean when a bond is non-polar?

A

the electron in the bond are evenly distributed

49
Q

how is a polar bond formed?

A

bonding atoms have different electronegativities

50
Q

why is H2O polar and not CO2?

A

CO2 is symmetrical so there is no overall dipole

51
Q

intermolecular force

A

attractive force between neighbouring molecules

52
Q

what are the 3 types of intermolecular forces?

A

hydrogen bonding, permanent dipoles, London forces

53
Q

permanent dipole-induced dipole interactions

A

when a molecules with a permanent dipole is close to other non polar molecules it causes the non polar molecule to become slightly polar leading to attraction

54
Q

permanent dipole-permanent dipole interactions

A

some molecules with polar bonds have permanent dipoles
forces of attraction between those dipoles and those of neighbouring molecules

55
Q

London forces

A
  • caused by random movements of electrons
  • leads to instantaneous dipoles
  • instantaneous dipole induces a dipole in nearby molecules
  • induced dipoles attract one another
56
Q

are London forces greater in smaller or larger molecules?

A

larger due to more electrons

57
Q

does boiling point increase or decrease down the noble gas group? why?

A

increases
the number of electrons increases and hence the strength of London forces also increases

58
Q

what conditions are needed for hydrogen bonding?

A

between hydrogen atom and a highly electronegative atom - O, N, F

59
Q

why is ice less dense than liquid water?

A

in ice the water molecules are arranged in an orderly pattern
it has an open lattice with hydrogen bonds
in water the lattice is collapsed and the molecules are closer together

60
Q

why does water have a higher melting/boiling point than expected?

A

hydrogen bonds are stronger than other intermolecular forces so extra strength is required to overcome the forces

61
Q

what type of intermolecular forces do alkanes have? why?

A

London force
induced dipole-dipole interaction becuase the bonds are non polar

62
Q

what happens to the boiling point as alkane chain length increases? why?

A

boiling point increases bc there is more surface area and so higher number of induced dipole-dipole interactions
therefore more energy required to overcome the attraction

63
Q

does a branched molecule have lower or higher boiling point compared to equivalent straight chain? why?

A

branched molecule has a lower boiling point bc they have smaller surface area and hence less induced dipole-dipole interactions

64
Q

are alkanes soluble in water?

A

insoluble because hydrogen bonds in water are stronger than alkane’s London forces

65
Q

what kind of intermolecular forces do alcohols have?

A

Hydrogen bonding due to the electronegativity difference in the OH bond
London forces

66
Q

how do alcohols’ melting point and boiling point compare to other hydrocarbons’ of similar C chain lengths?

A

higher due to hydrogen bonding being stronger than London forces

67
Q

are alcohols soluble in water? why does solubility depend on chain length?

A

soluble when short chain - OH hydrogen bonds to hydrogen bond in water
insoluble when long chain - non-polar C-H bond

68
Q

explain the trend of boiling temperatures of hydrogen halides HF to HI

A

general increase of boiling point from HCl to HI which is caused by increasing London forces becuase of increasing number of electrons
there is a big drop from HF to HCl becuase F is very electronegative therefore the hydrogen bonding is much stronger

chemistry 2 (22 decks)

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