Chromium/copper: s moves to d to make single orbitals
Ion structures
REMEMBER
Ionisation Energy
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Factors
more protons = more IE
More distance from nucleus = less IE
More shielding/screening = less IE
paired electrons = less IE
A few elements
Hydrogen
Helium
Lithium
General trends
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Exceptions
group 2-3 (Be - B)
group 5-6 (N-O)
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Zinc
Activation energy
next IE's
Used to find group
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hydrogen emission spectrum
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Finding the series limit graphically
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Electron Affinity
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Group 7 elements
F -328 kJ mol-1
Cl -349 kJ mol-1
Br -324 kJ mol-1
I -295 kJ mol-1
less reactive as you move down
Second affinty
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Atomic and Ionic radius
Left: Metallic radius/covalent radius, Right:van der Waals radius
Metallic because thats how it is in metals and covalent bonds.
Van der Waals because of the weak attractions taking place
Trends: Leaving the noble gases out, atoms get smaller as you go across a period.
This happeneds because protons make it tighter whilst screening stays the same
Hybridised
Transition elements
When filled, 4s is actually higher than 3d
Ionic radius
Bonding
Ionic Bonding
Electrons move from one atom to another
Cations
Anion
Examples
Magnesium Oxide MgO
Calcium Chloride CaCl2
Potassium Oxide K2O
Noble gas structures
Positive ions with noble gas structure
Negative ions with noble gas structure
Its NOT about becoming noble
Instead its about the release of energy over the entire reaction
It take IE for each cation and it give energy for stronger bonds
So the reaction that happens will be the one where (total IE + evolved energy) is greatest
Single Covalent Bonding
the nucleus of both atoms attract the shared pair
hydrogen
hydrogen chloride
complex
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Promotion of electrons
atom is in an excited state
so in actual fact, the atoms will try to form as many bonded pairs as it can.
Hybridisation
sp3
atoms merge with new molecular orbit
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promotion happens within an energy level
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In PCl3 and 5 its more profitable for the P to promote electrons thus enabling more bonds
NCl5 doesnt exist because the promotion from 2s2 would have to be to 3s which is too great
sharing the GCSE "noble" view
Double Covalent Bonding
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Sophisticated view of the bonding in Ethane
First promotion in carbon from 2s2 to 2px
Next, hybridisation allows s and p to form 4 bonds
Double bonds with each carbon, and 2 hydrogen single bonds
Types of structure
Ionic Structures
Sodium Chloride lattice
this is called a 6:6-co-ordinated because each atom touches 6 others
6:6 co-ordinated happens because we dont want same atoms to touch and cause repulsions
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sometimes simplified versions are drawn
The more ions surrounding each makes it more stable
size ratio causes this not to happen
Radius Ratio
anion is >73%(cation) = 8:8
41% < anion <73% = 6:6
anion < 41% = 4:4
Physical Properties of NaCl
High melting and boiling point
More charges on ions make stronger bong
smaller ions hold together better
Brittle
This is because they repel each other apart given some stress
Soluble in water (typical of ionic solids)
attractions from the loan pair in oxygen attract the positive ions
which can pull them apart to form co-ordinate (dative covalent) bonds
Insoluble in organic solvents
Electrical behaviour
When melts undergoes Electrolysis
this is a Chemical change rather than physical
Process:
Na+ moves towards the cathode to collect an electron. returning it to Na
Cl- moves towards the anode to give an electron returning it to Cl (and then 2Cl)
External circuit
the battery keeps filling the the cathode with electrons after they have been taken