Giant Structure Flashcards
Name 3 methods of proving ion existence
Electrolysis
Ion migration
X-ray crystallography
How does electrolysis prove ion existence
aq/l
Conduct electricity
Free delocalised electrons to carry charge
How does ion migration prove ion existence
aq coloured ions
Copper chromate solution soaked paper
Crocodile clips, DC power supply
Blue copper cations, yellow chromate anions
How does X-ray crystallography prove ion existence
Diffract through slag crystal
Electron density map
Contours link equal charge regions
Separate ionic solid entities
Lattice energy
Energy change to make 1 mole of a solid ionic crystal from its gaseous ions
Exo
Standard enthalpy change of formation
Energy change to make 1 mole of a compound from it’s elements in their standard state under standard conditions
Standard enthalpy change of atomisation
Energy change to make 1 mole of gaseous atoms from it’s elements in their standard state under standard conditions
Endo
Ionisation energy
Energy to remove 1 electron from each atom/ion in 1 mole of gaseous atoms/ions
Endo
Electron affinity
Energy change to add 1 electron to each atom/ion in 1 mole of gaseous atoms/ions
Describe the energetics pattern of electron affinity
From neutral = exo
From negative = endo
Negative charge of ion and negative charge of electron repel each other, energy must be absorbed to overcome the ESR
Describe the 3 general layers of a borne haber cycle
Natural elements
Gaseous ions
Solid lattice
Describe the differences (4) between a BHC of NaCl and MgCl2
Higher IEs
Higher No.IEs
Higher lattice enthalpy
Double Cl values
Name 3 factors that effect LE
Charge of ions
Size of ions
No. Ions
BHC exam technique terminology
X larger/smaller
More Endo/exo
State what is
How does charge effect LE
Higher charge
Higher ESA between ions
Higher ETO
More exo LE
How does ion size effect LE
Larger size
Ions further away
Less ESA
Less exo LE
Exam technique factors effecting LE
State what’s the same and what’s different
What’s influences theoretical LE
Ion attraction/repulsion
How do you calculate the theoretical LE
Charges + distance between ions —> sum of forces
Describe 3 reasons why theoretical LE is calculated
BH experimental data doesn’t exist
Use in BH to find (usually) less exo enthalpy of formation for unexpected compounds
Compare T + E, find validity, more than 10% difference = insufficient model, usually covalent bonding present
Describe metallic bonding structure
Close packed giant lattice of positive ions and a sea of delocalised electrons
Held together by ESA between positive ions and negative electrons
Name 3 properties of metallically bonded structures
High mp/bp
Malleable
Electrical conductor
Why are metallic structures malleable
Same layers
Movement doesn’t change bonding
Why are metallic structures electric conductors
Delocalised electrons from ions carry charge through substance
Why do metallic structures have high mp/bp
Giant structures
Many strong bonds
More ETO
Enthalpy change of solution
Enthalpy change for 1 mole of a substance to dissolve in water to become a solution of infinite dilution
Enthalpy change of hydration
Enthalpy change for 1 mole of gaseous ions to dissolve in water to become a solution of infinite dilution
Describe the appearance of a hydrated ion
Ion surrounded by opposite charge atoms of water molecules
Describe what happens when an ionic solid dissolves in water
Crystal lattice broken (endo)
Water H bonds broken (endo)
H point at cation
O point at anion
ESA (exo)
Hydration
Describe a hydration cycle
Gaseous ions at top
Aqueous ions in middle
Solid lattice at bottom
Why is finding the enthalpy of solution from a hydration cycle unreliable (4)
- Small difference between 2 much larger values that can’t be directly found and are effected by charge and size factors
- Small % uncertainty in LE of hydration enthalpy can —> large solution enthalpy % uncertainty
- Solution enthalpy isn’t only solubility factor, endo solution enthalpy won’t dissolve well, large LE
- Soluble compounds can form saturated solution
Why does poor E + T LE agreement occur
Polarisation of anion by cation
Cation distorts electron cloud on anion
Pulls towards shared region
Nearly electron sharing
Some covalent character
Stronger bonding
ELE more exo than TLE suggests
Anion and cation properties in polarisation
Cation, polarising power
Anion, polarisability
What factors INCREASE polarising power of cation
Increase cation charge
Decrease cation size
Higher positive charge density = more effective distortion
What factors INCREASE polarisability of anion
Increase charge
Increase size
Larger ion = less grip on outer electrons = easier to distort
Name 4 levels on bonding spectrum
Pure covalent
Polar covalent (unequal shared electrons)
Polar ionic (distorted ions)
Pure ionic
Name 3 allotropes of carbon
Diamond
Graphite
Graphene
Graphite 4 properties 2 uses
- Conductor, delocalised electrons between layers
- Sheet formation
- Each C bonded to 3 others
- Soft, layers can slide
Uses, electrics, pencils
Diamond 7 properties
- All Cs cov bonded to 4 others
- Tetrahedral structure
- High mp, lots ETO, many bonds
- Hard, strong bonds, lattice arrangement
- Thermal conductor, vibrations travel through stiff lattice
- Insoluble, more attracted to neighbouring atoms that solvent molecules, no ions
- Not electrical conductor, no free electrons/ions
Graphene 6 properties
One sheet of graphite, joined by 2 hexagons
2D, one atom thick
Conductor, delocalised electrons
Strong
Transparent
Light
