A summary of topic 2, organised so the notes are easy to understand. The notes are on slides, so they can be printed out and used as revision cards or posters, for revision on the go. The notes cross-reference the specification so it is easy to see where each bit of information has come from. They ...
Metallic bonding Ammonia + HCl
= strong electrostatic attraction between metal cations and NH3 + HCl → NH4Cl (solid ∴ thick white smoke)
the sea of delocalised electrons NH3 + HCl → NH4^+ + Cl^-
Ionic bonding H+ leaves its e- w/ Cl (making it -ve) and moves to the lone
= the strong electrostatic attraction between 2 oppositely pair on the N (making NH3→NH4^+)
charged ions Aluminium chloride:
Stronger attraction between ions = stronger bonds
Al2Cl6 sublimes at 180°C (quite low)
Forces of attraction determined by:
CHARGE ∴ covalent
- Length of bond (AKA size of ion)
DENSITY Mr shows Al2Cl6 is Al2Cl6, and not AlCl3
- Charge on ions
Stronger bond = ↑ charge, small ion
- Cations are smaller than their atoms Bond energy and length:
- Anion are larger than their atoms Bond energy = the energy required to break 1 mole of a
Ionic radii: particular covalent bond in the gaseous state, kJ/mol
- Down a group, radii ↑ due to ↑ shells - ↑ bond energy = stronger bond
- Across a period, radii ↑ w/ ↑ -ve charge Bond length = the distance from the nucleus of one atom to
radii ↓ w/ ↑ +ve charge another, which forms the bond
(more -ve = bigger) - ↑ forces attraction = atoms pulled together = ↓ bond
Evidence for ionic bonding: length = ↑ strength of bond
- Electrolysis of CuCrO4 Strong bond = big bond energy & small bond length
Blue Cu^2+ (cations) to cathode Electronegativity:
Yellow CrO4^2- (anions) to anode = the ability of an atom to attract a BP of electrons in a
- Electrolysis of KMnO4 (purple) on filter paper covalent bond
Purple MnO4^- (anion) to anode ↑ across a period
Covalent bonding ↓ down a group
= the strong electrostatic attraction between a shared pair of Affected by atomic number & distance of valent e- from
electrons & the nuclei of the bonding atoms nucleus
Dative covalent bonding Polar bonds:
= one atom contributes both e-’s in a bond e.g. In a covalent bond w/ 2 different electronegativities, the BP of
e-’s will be puller towards the more EN atom (polar)
, Shapes of molecules: TRIGONAL
- Max separation, min repulsion PLANAR
- LP’s repulse more than BP’s BP = 3
LP-LP > LP-BP > BP-BP LP = 0
120°
LINEAR
BP = 2
LP = 0
180°
TETRAHEDRAL
BENT (V-
BP = 4
SHAPED)
LP = 0
BP = 2
109.5°
LP = 1
118°
TRIGONAL
TRIGONAL BIPYRAMIDAL
PYRAMIDAL BP = 5
BP = 3 LP = 0
LP = 1 120° & 90°
107°
OCTAHEDRAL
BP = 6
BENT (V- LP = 0
SHAPED) 90°
BP = 2
LP = 2
104.5°
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