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a-level chem (aqa) > 3.1.3: Bonding > Flashcards

3.1.3: Bonding Flashcards

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1
Q

Why do elements bond to have a full outer shell?

A
  • to become more stable
  • to be inert and unreactive
  • like noble gases
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2
Q

What is ionic bonding?

A
  • ions attatched due to an electrostatic attraction between opposing charges
  • between metals and nonmetals
  • lose or gain electrons
  • metal= positive ion/cation
  • non-metal= negative ion/ anion
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3
Q

What are properties of ions?

A
  • dissolve in polar solvents
  • always solid at room temperature due to strong ionic bonds and electrostatic forces
  • in a fixed position when solid, can vibrate but can’t carry current /electricity.
  • when molten, ions are free to move and carry electrical current
  • brittle as layers can move in alternating positive/negative ions that can repel to break apart the ion
  • high melting and boiling point
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4
Q

What is covalent bonding?

A
  • bond between 2 nonmetals
  • share electrons
  • single covalent bond= one shared electron pair
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5
Q

What are properties of covalently bonded molecules?

A
  • held by electrostatic attraction between nucleus of atom and shared electrons
  • low melting and boiling points due to weak intermolecular forces so little energy is needed to break them apart
  • strong coval nt bonds
  • poor conductors of energy due to neutral charge
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6
Q

What’s a co-ordinate/ dative bond?

A
  • a type of covalent bond
  • both electrons from a pair come from one atom, represented by an arrow
  • atom that accepts electrons doesn’t have a full outer shell and is electron deficient
  • donating atom donates non-bonding pair of electrons (lone pair)
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7
Q

What is a metallic bond?

A
  • metal merges the main levels of its atoms
  • electrons aren’t associated with a single atom but shared
  • positive ions surrounded by delocalised electrons
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8
Q

What’s the arrangement of metallic structures?

A
  • arranged metal ion in latttice
  • results in giant metallic structure of positively charged ions
  • sea of delocalised electrons
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9
Q

What are the properties of metallic structures?

A
  • good conductor of heat/ electricity (have delocalised electrons which can vibrate and carry charge).
  • very strong (the greater charge, the more delocalised electrons, the more it vibrates)
  • malleable and ductile (even aftervsmall distortion, layers still in same place)
  • high melting and boiling point (giant with strong attraction)
  • +ionic charge, -ion size,+no. valence electrons, +attraction, +mp. and bp.
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10
Q

What is periodicity?

A

The electrons on the outer shell and reaction patterns across elements.

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11
Q

What is electronegativity?

A

the ability and power of an atom to attract a pair of electrons and towards it

the greater electronegativity the more electrons it attracts

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12
Q

What are factors affecting electronegativity?

A
  • nuclear charge (greater charge, increases attraction of electrons due to opposing charge)
  • distance of the valence shell from the nucleus
  • electron shielding (less shielding, less distance)
  • the more electronegative, the greater share of electrons in polar atoms (e.g. Cl is more e.n. so in HCl electrons pull towards Cl)
  • so HCl is a polar covalent bond as its not a symmetrical distribution of charge (permanent as Cl is always more e.n. than H)
  • greater diffence in e.n., greater permanent dipole
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13
Q

Who is Linnaeus Pauling?

A

The scientist who made the Pauling scale used to measure electronegativity based on trends in shielding, shells, attraction and distance.

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14
Q

What is VSEPR theory?

(valence shell) electron pair repulsion theory

A
  • as electron pairs in the same outer shell have the same charge, they repel and spread as far apart as possible
  • one spins upwards, other spins downwards, minimising the repel
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15
Q

What is electron domain?

A
  • each pair of shared electrons behaves as a single unit in terms of repulsion as they’re found together.
  • single, double, triple and lone pairs act as one domain
  • the total no. of electron domains determines molecule shape
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16
Q

What is the effect of lone pairs?

A
  • slightly more electron dense than a bonded pair
  • repel more than bonding pairs
  • reduce bond angle by 2.5° per lone pair
17
Q

What are the differnt types of bonds based on differences in electronegativity?

A
  • no difference in electronegativity= non-polar covalent
  • small difference in electronegativity= polar covalent
  • large difference in electronegativity= ionic bond
18
Q

What’s the difference between molecular and electron domain geometry?

A

Molecular geometry- considers bonded domains only
Electron domain geometry- considers all domains

if there’s lone pairs on the central atom, eg and mg won’t be the same

19
Q

VSEPR GEOMETRY

molecular geometry of 2 domains

A

linear= 180°

20
Q

VSEPR GEOMETRY

molecular geometry of 3 domains

A

trigonal planar= 120°
- 1 lone pair- bent(117.5°)

21
Q

VSEPR GEOMETRY

molecular geometry of 4 domains

A

tetrahedral= 109.5°
- 1 lone pair- trigonal pyramidial (107°)
- 2 lone pairs- bent (104.5°)

22
Q

VSEPR GEOMETRY

molecular geometry of 5 domains

A

trigonal bipyramidial= 120° & 90°
- 1 lone pair- seesaw
- 2 lone pairs- T shape
- 3 lone pairs- linear (180°)

23
Q

VSEPR GEOMETRY

molecular geometry of 6 domains

A

octahedral= 90°
- 1 lone pair- square pyramidial
- 2 lone pairs- square planar
- 3 lone pairs- T shape
- 4 lone pairs- linear (180°

24
Q

What are intermolecular forces?

A
  • forces that hold atoms together, to do with attraction between positive and negative
  • in ionic compounds, this is caused by the complete transfer of electrons.
  • not all i.m. forces are equal
  • VDW, dipole, hydrogen bonds (increase in strength)

intermolecular forces are weaker than cova!ent bonds

25
Q

What are Van Der Walls forces?

instantaneous, induced, temporary dipole

A
  • uneven distribution of electrons (as electrons are constantly moving)
  • if more happen to be on one side than the other, a temporary/ instantaneous dipole is created (one more electronically charged than the other/ electron distortion)
  • this can induce the neighbouring atom
  • the more electrons, the greater charge, the stronger the VDW

occur between all molecules, even if there’s other intermolecular forces

26
Q

What is a permanent dipole?

A
  • there’s only permanent dipole-dipole attraction between polar molecules
  • molecules with polar bonds but are non-polar don’t have this attraction

e.g. HCl

27
Q

What’s a polar molecule?

A
  • a molecule that contains polar bonds that are arranged asymmetrically around the central atom so the charge is unevenly distributed
  • therefore polar molecules have a permanent dipole, in addition to the weaker VDW forces by a temporary dipole
28
Q

What is polarity?

A
  • an unequal sharing of electrons in a bond, if the electron sharing is equal, the bond is described as non-polar
  • this increases melting and boiling point
29
Q

What is hydrogen bonding?

a special case of permanent dipole-dipole attraction

A
  • A hydrogen (H) atom bonded to a very electronegative atom (e.g. F,O and N)
  • the polar bond between the H and electronegative atom leaves the H nucleus exposed as H only has one electron
  • therefore, there’s a strong attraction from the lone pair on the electronegative atom of one molecule to the exposed H nucleus of another molecule

Hydrogen- slightly positive, Electronegative molecule- slightly negative

30
Q

What is a melting and boiling point?

A

melting- temperature where a solid melts to be liquid
boiling- temperature where liquid changes and boils to be a gas

(this can be represented on a graph with specific heat of fusion and vapourisation)

31
Q

Solid properties

arrangement, spacing, movement

A

ARRANGEMENT- fixed regular arrangement, crystal shaped have straight edges/ definite shapes.
SPACING- compact and close, not easily compressed
MOVEMENT- vibrate around a point

32
Q

Liquid properties

A

ARRANGEMENT- random, changes shape to fit container, compact
SPACING- close, not easily compressed
MOVEMENT- rapid ‘jolting’

33
Q

Gas properties

A

ARRANGEMENT- random, changes shape to sealed container
SPACING- far apart, easily compressed
MOVEMENT- rapid, gases exert pressure

34
Q

What is a crystal?

A
  • solid particles with a regular arrangement, held together by forces of attraction
    -the strength of the forces of attraction between particles in the crystal affects their physical properties

forces can be strong (ionic, covalent or metallic) or weak (VDW,d-d,h)

35
Q

What’s an example of a crystal?

A
  • graphite- high m.p., soft due to VDW, conductor, graphene layers that slide, delocalised electrons
  • diamond- very high m.p., strong, rigid
  • silica (SIO4)

all crystals joined by covalent bonds have a high m.p. due to lots of covalent bonds and don’t conduct electricity (except graphite) as there’s no free electrons

covalent, giant, macro = all th same giant molecules

a-level chem (aqa) (15 decks)

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