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ib - chemistry > 4. Chemical bonding and structure > Flashcards

4. Chemical bonding and structure Flashcards

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1
Q

an ionic bond is an … between oppositely charged ions

A

electrostatic attraction

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2
Q

ionic compounds usually have … melting points and boiling points due to the strong e-static forces of attraction between positively charged ions

A

high

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3
Q

ionic solids have … volatility

A

low

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4
Q

ionic substances … conduct electricity when solid

A

do not

only conduct when liquid/aqeous

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5
Q

water is a … solvent, hence ionis substances are often … in water

A

polar

soluble

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6
Q

covalent bonding occurs when

A

atoms share electrons

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7
Q

a covalent bond is

A

the electrostatic attraction between a shared pair of electrons and the nuclei of the atoms that are bonded

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8
Q

more bonds → … strength

A

more

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9
Q

electronegativity is a measure of

A

the attraction of an atom in a molecule for the electron pair in the covalent bond of which it is a part

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10
Q

atoms with similar electronegativities will form

A

covalent bonds

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11
Q

atoms with widely different electronegativities will form

A

ionic bonds

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12
Q

non-metals have … electronegativities than metals

A

higher

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13
Q

to remember the trends in electronegativity, just remember that fluorine is the atom with the highest electronegativity

electronegativity must then … across a period towards fluorine and … down a group from fluorine

A

increase

decrease

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14
Q

bonding between

two elements is ionic if the difference is more than …, and covalent if the difference is less than …

A

1.7

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15
Q

a coordinate covalent bond is a type of covalent bond in which

A

both electrons come from the same atom

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16
Q

VSEPR theory

A

pairs of electrons (electron domains) in the valence (outer) shell of an atom repel each other and will therefore take up positions in space to minimise these repulsions – to be as far apart in space as possible

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17
Q

the order of repulsion strength for pairs of electrons is:

A

lone pair–lone pair > lone pair–bonding pair > bonding pair–bonding pair

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18
Q

diamond

A

giant covalent structure
tetrahedral arrangement
high mp and bp
do not conduct e-

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19
Q

graphite

A

covalent structure
layer structure
trigonal planar array
london forces between layers
conducts e-, e- can move in between layers

20
Q

graphene

A

tensile strength
high melting point because covalent bonds need to be broken to break the sheet
good e- and heat conductor

21
Q

C60 fullerene

A

giant structure
consists of individual C60 molecules, with covalent bonds within the molecule and London forces between the molecules

22
Q

silicon dioxide

A

giant covalent structure
tetrahedral array

23
Q

van der waals’s forces

A

name given to the forces
between molecules and includes London (dispersion) forces, dipole−dipole interactions and dipole-induced dipole interactions

24
Q

london forces are

A

temporary (instantaneous) dipole–induced dipole interactions

25
Q

london forces get stronger as

A

the relative molecular mass increases

26
Q

if molecules with similar relative molecular masses are compared, polar molecules have … melting and boiling points than non-polar molecules.

A

higher

27
Q

dipole-dipole attractions

A

polar molecules

28
Q

the requirements for hydrogen bonding are that the H atom is attached to

A

a very electronegative atom – N, O or F – which possesses at least one lone pair of electrons

29
Q

hydrogen bonding is … than covalent bonding

A

weaker

30
Q

strength of intermolecular forces of attraction

A

London < permanent dipole–dipole <
hydrogen bonding

31
Q

substances that are able to participate in hydrogen bonding will generally be … in water

A

soluble

they are able to hydrogen bond to the water

32
Q

metallic bonding is

A

the electrostatic attraction between the positive ions in the lattice and the delocalised electrons

33
Q

properties of metals

A

lustrous
good conductor of e-
good conductor of heat
ductile
malleable

34
Q

alloys are

A

homogeneous mixtures of two or more metals, or of a metal with a non-metal

35
Q

formal charge close to 0 means

A

even distribution of charge
stable structure

36
Q

FC=

A

FC=(nb valence e- in the uncombined atom) - 1/2 (number of bonding electrons) − (number of non-bonding electrons)

37
Q

sigma bond

A

result from the axial (head-on) overlap of atomic orbitals

38
Q

pi bond

A

formed by the sideways overlap of parallel p orbitals

39
Q
  • a single bond consists of a … bond
  • a double bond consists of a … bond and a … bond
  • a triple bond consists of a … bond and two … bonds
A
  • a single bond consists of a σ bond
  • a double bond consists of a σ bond and a π bond
  • a triple bond consists of a σ bond and two π bonds
40
Q

delocalisation is

A

the sharing of a pair of electrons between three or more atoms

41
Q

a single bond is said to have a bond order of …, a double bond has bond order … and a triple bond has bond order …

A

1,2,3

42
Q

hybridisation rule

A
  • when a carbon atom forms
    just single bonds, the shape is tetrahedral and the hybridisation is sp3
  • when a carbon atom forms a double bond, the shape
    is trigonal planar and the hybridisation is sp2
  • when a carbon atom forms a triple bond, the shape is linear and the hybridisation is sp
43
Q

hybridisation is

A

the mixing of atomic orbitals in a particular atom to produce a new set of orbitals (the same number as originally) that have characteristics of the original orbitals and are better arranged in space for covalent bonding

44
Q

destruction of ozone by chlorofluocarbons

A

CCl2F2 → (UV) CClF2 + Cl
Cl+O3 → ClO+O2
ClO+O→O2 + Cl*

O3 + O* → 2O2

a C–Cl bond is weaker than a C–F bond and undergoes homolytic fission more readily
the chlorine free radical released in this process can take part in a chain reaction, which uses up ozone and regenerates chlorine free radicals, Cl* to react with more ozone

45
Q

destruction of ozone by nitrogen oxides

A

N2O(g) + O(g) → 2N O(g)
*NO2(g) + *O(g) → NO(g) + O2(g)
O3 + O → 2O2

NO is a catalyst in this reaction - it is used up in the first step but regenerated in the second step - overall it is not used up

ib - chemistry (11 decks)

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