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chemistry > 04 - chemical bonding > Flashcards

04 - chemical bonding Flashcards

1
Q

what are cations?

A

a positively charged ion

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2
Q

what are anions?

A

a negatively charged ion

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3
Q

what is a lattice?

A

a regularly repeating arramgement of atoms, molecules or ions in three dimentions throughout the whole crystal structure

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4
Q

what are the van der Waals’ forces?

A
  • weak forces of attraction between molecules involving either id-id or pd-pd (+ hydrogen bonding)
  • a general term to describe all intermolecular forces (weak forces between molecules)
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5
Q

types of van der Waals’ forces?

A
  • instantaneous dipole-induced dipole (id-id) AKA. London dispersion forces
  • permanent dipole-permanent dipole (pd-pd)
  • hydrogen bond (a stronger form of pd-pd)
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6
Q

what are intermolecular forces?

A

the weak forces between molecules

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7
Q

Positive ion?

A

CATIONS
- loss of electrons
- usually metals
- to negative cathode

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8
Q

negative ion?

A

ANION
- gain of electrons
- usually non metal
- to positive anode

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9
Q

what is an ionic bond/electrocovalent bond?

A

the elctronstatic attraction between oppositely charged ion (cations and anions)

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10
Q

what are dot and cross diagrams?

A
  • a diagram showing the arrangement of the outer shell electrons in an ionic or covalent element or compound
  • electrons shown as dots or crosses to show their origin

shows:
. outer shell electrons in pairs
. charge of ion spread evenly
. square bracket
. ion charge art top right hand corner
. if more than two atoms types, uses circle, triangle, star, etc

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11
Q

what is a covalent bond?

A

the electrostatic attractions between the nuclei of two atoms and a shared pair of electron

represented by a single line between two atoms

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12
Q

what are lone pairs?

A

pairs of electrons in the outer shell of an atom that are not involved in bonding

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13
Q

what are the cases where covalently bonded compounds don’t have a noble gas configuration (electron octet)?

A

. BORON TRIFLURIDE (BF3) - electron deficient (6 electrons)

. SULFUR HEXAFLURIDE (SF6) - expanded octet (12 electrons)

. PHOSPHORUS (V) CHLORIDE (PCl5) - expanded octet (12 electrons)

. SULFUR DIOXIDE (SO2) - expanded octet (10 electrons)

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14
Q

what is a double covalent bond?

A

two shared pairs of electrons bonding two atoms together (two line)

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15
Q

what is triple covalent bond?

A

three shared pairs of electrons bonding two atoms together (3 lines)

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16
Q

what is a co-ordinate bond/ dative covalent bond?

A

the sharing of a pair of electrons between two atom where both electrons in the bond come from the same atom

need:
. one atom with lone pair of electrons
. a second atom to have an unfilled orbital to accept the lone pair (an electron deficient compound)

eg:
. NH4+
. Al2Cl6

diplayed by arrow pointing away from lone pair

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17
Q

what is bond energy?

A

the energy required to break one mole of a particular covalent bond in the gaseous state

used to measure the strength of a bond

units = kJ mol-1

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18
Q

what is bond length?

A

. the distance vetween the nuclei of two covalently bonded atoms

. more bond strength = less reactive

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19
Q

why are double bonds shorter and have more energy than single bonds?

A

. more quantity of nuclear charge between two atomic nuclei

. more force

. more attraction

. more bond strength

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20
Q

factors affecting the reactivity of a molecule?

A

. bond polarity
. bond strength
. whether bond is sigma or pi

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21
Q

what does VESPR stand for?

A

Valence Shell Electron Pair Repulsion theory

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22
Q

what does VESPR stand for?

A

Valence Shell Electron Pair Repulsion theory

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23
Q

what does the VESPR theory state?

A

. valence shell electrons are the elctrons in the main outer shell

. electron pairs repel each other since they have the same charge

. lone pairs repel more than bond pairs

. double bond repulsion > multiple single or single bond repulsion

. shape of a molecule can be deduced using this theory

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24
Q

what is the order of repulsion between pairs?

A

lone-lone > lone-bond >bond-bond

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25
why do lone pairs repel more than bond pairs?
lone pairs have more concentrated electron charge clouds, and they are both wider and closer to the nucleus
26
what is the shape and angle of methane?
tetrahedral, 109.5°
27
what is the shape and angle of ammonia?
pyramidal, 107°
28
what is the shape and angle of water?
nonlinear V shape, 104.5°
29
what is the shape and angle of boron trifluoride?
trigonal planar, 120°
30
what is the shape and angle of carbon dioxide?
linear, 180°
31
what is the shape and angle of phosphorus pentafluoride?
trigonal bipyramidal, 120° and 90°
32
what is the shape and angle of sulfur hexafluoride?
octahedral, 90°
33
what is molecular orbital?
combined orbital formed from the overlap of atomic orbitals ina covalent bond, contains 2 atoms greater the overlap, stronger the bond
34
what is hybridisation?
the mixing of atomic orbitals
35
hybridiasation: what s and what p make what?
. s + one p = sp hybrid orbitals . s + two p = sp² hybrid orbitals . s + three p = sp³ hybrid orbitals
36
per atom, number of lone pair + number of sigma bonds
2 - sp 3 - sp² 4 - sp³
37
what is a sigma bond?
head on overlapping of orbitals, electrons delocalised, forms stronger bonds
38
whta are pi bonds?
lateral overlapping of orbitals, electrons more delocalised, forms relatively weaker bonds
39
how many sigma and pi bonds in a SINGLE bond?
1 sigma
40
how many sigma and pi bonds in a DOUBLE bond?
1 sigma bond, 1 pi bond
41
how many sigma and pi bonds in a TRIPLE bond?
1 sigma, 2 pi
42
what is metallic bonding?
the electrostatic sttraction between positive ions and delocalised electrons, STRONG, atoms packed in a lattice
43
what are delocalised electrons?
electrons that are not assiciated with any particular atom - IN METALS they move throughout the metallic structure between the metal ions when a voltage is applied
44
what is a lattice?
a regular arrangement where atoms are packed closely together
45
more metallic bonding...
. more positive charge on ions in the metallic lattice . less size of metal ions in the lattice . more number kf mobile electrons per atoms
46
what are the properties of metals?
. high melting and boiling points . strong attractions between ions and electrons . conduct electricity . conduct heat
47
what is electronegativity?
the power/tendency of a particular atom that is covalently bonded to another atom to attract the bonding pair of electoens towards itself
48
across a period, electronegativity...
increases
49
up a group, electronegativity...
increases
50
most electronegative element?
fluorine
51
least electronegative element?
caesium
52
what factors influence electronegativity?
. NUCLEAR CHARGE - same period with more nuclear charge, more electronegativity . ATOMIC RADIUS - same group atoms with more outer electron distance from nucleus, less electronegativity . SHIELDING - more inner electron shells and sub shells, less electronegativity
53
oxygen electronegativity value?
3.5
54
carbon electronegativity value?
2.5
55
what is the Pauling electronegativity scale?
a commonly used scale of electronegativity values symbol = Np units = none
56
high electronegativity value difference = ?
ionic compound
57
low electronegativity value difference = ?
covalent bond
58
what does non polar mean?
when the electronegativity values of the two atoms forming a covalent bonds are the same (eg H2, Cl2, Br2)
59
what happens in a non polar molecule?
when a covalent bond is formed between two atoms having different electronegativity values MORE ELECTRONEGATIVE ATOM ATTRACTS THE BOND PAIR TOWARDS IT thus: . centre of positive charge doesn't coincide witht he negative charge . asymmetric electron distribution . both atoms partially charged . less electronegative has delta positive sign . more electronegative have delta negative sign . say that bond is polar/has a dipole
60
what is dipole moment?
the product of the magnitude of the charge and the distance between the centres of the positive and negative charges used to measure the degree of polarity of a molecule shown with arrow, head pointing to partially negative end
61
can determine charge distribution by
X ray spectroscopy
62
more polar =? reactive
more reactive
63
id-id
instantaneous dipole - induced dipole forces . weakest intermolecular attractive force . results from temporary id id forces in both polar and non polar molecules
64
more id id :
. more electrons . more number of contact point . more boiling point . more strength
65
what are pd-pd forces?
permanent dipole - permanent dipole attractive intermolecular forces which result from permanent dipoles in molecules . molecules with a permanent dipole are called POLAR MOLECULES . often stronger than id id . often higher boiling point than id id
66
what is hydrogen bonding
. strong type of pd pd force . the strongest form of intermolecular bonding . weaker than covalent bond
67
what is the requirements for hydrogen bonding to occur?
. H atom covalently bonded to highly electronegative (eg N, F, O) . another highly electronegative with a lone pair of electrons
68
properties of water?
. more boiling point (more hydrogen bonding) . more enthalpy change of vaporisation (more hydrogen bonding) . high surface tension (hydrogen bonds exert a significant downward force at the liquid surface) . more viscosity (hydrogen bonding reduces ability of water molecules to side over each other) . more dense than ice (rigid lattice with each O atom surrounded by H atoms, long bond lengths, more apart than in liquid)
69
IONIC COMPOUNDS?
. solid at rtp . high mp, bp, high enthalpy changes vaporisation . soluble in water . don't conduct when in solid state
70
METAL PROPERTIES?
. solids (not mercury) . high mp, bp, high enthalpy changes vaporisation . insoluble in water . conduct in solid and molten
71
COVALENT COMPOUNDS PROPERTIES?
. solid, liquid, gas . some insoluble, some soluble . some react not dissolve . don't conduct electricity

chemistry (19 decks)

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