(I) Topic 17 - Thermodynamics
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Why is the first Electron Affinity Exothermic but the Second Electron Affinity Endothermic
During the second electron affinity, there must be an input of energy for the second electron to overcome the repulsion against the first electron, and join to the ion - this makes it Endothermic.
What is the perfect ionic model?
The model assumes that all ions are perfect spheres with no ionisation or covalent character.
Factors affecting enthalpy of lattice dissociation and formation
Size of ions - Smaller the ion the stronger the bonding Charge of ions - Higher charge = stronger bonding
What is covalent character?
Ionic compounds are polarised, meaning they are often distorted and not perfectly spherical. If there is a lots of distortion, the compound is still ionic but is said to also have covalent character.
What is the: 2nd Law of Thermodynamics
Entropy will increase naturally over time
What is the:: 3rd law of thermodynamics
The entropy of a substance is zero at absolute zero and increases with temperature