Solids

solids

particles in very close contact

• strongest intermolecular forces

• amorphous - disorganized clusters with no-long range order

• crystalline - highly ordered lattice-like assemblies

Properties of crystallines: non polar

• consists of atoms or non polar molecules

• dispersion forces

• low to moderate melting point

• non polar solvents

Properties of crystallines: polar

• consists of polar molecules

• dispersion forces, dipole-dipole and dipole-induced dipole

• low to moderate melting point

• some non polar and some polar solvents

Properties of crystallines: hydrogen bonded

• consists of molecules with H bonded to N, O, or F

• hydrogen bonds

• low to moderate melting point

• some hydrogen-bonded and some polar solvents

allotropes

polymorphic forms of the same element

• have different molecular structures (connectivities)

diamonds

• tetrahedral

• melting point > 3500 degrees celsius (need to break C-C bonds)

• nonconductor since electrons are localized in bonds (not mobile)

graphite

• planar

  • similar geometry to benzene

• large distances between layers means they can slipover each other easily

• delocalized electrons means it conducts electricity

• stay together due to high stacking (strong, non-covalent attractions between flat, electron-rich aromatic rings

Ionic bonding

• bond strength is related to lattice energy

• coulomb’s law: F: k (q₁ x q_2)/ r²

• generally increases as the charge on the ions increases, and as the distance between the ions decreases

lattice energy

primarily responsible for the thermodynamic advantage of forming ionic solids

• can use this trend and electrostatic charges to predict the relative strength (stability)

born hater cycle

process to calculate the lattice enthalpy (energy) of an ionic compound by breaking its formation from elements into several known enthalpy steps, like sublimation, ionization, bond dissociation, electron affinity, and formation enthalpy

crystalline structures

• crystals are generally made up of regular repeating arrays called lattices

  • packed in such easy as to make best use of space

• unit cell - “element” that repeats in the lattice

  • can be atoms, ions, or molecules

• coordination number - how many items a given particle is in contact with in a unit cells

crystal lattices

• 14 different types

• lengths (abc,)

• angles (alpha, beta, gamma)

• different types of symmetry

• cubic has the greatest agree of symmetry (a=b=c, alpha=beta=gamma=90^o)

cubic arrangements: single unit cubic cells

• has its constituents only at the ends (corners) of a cub

cubic arrangements: body centered cubic (bcc)

• has its constituents at the ends (corners) of a cube

• has an additional constituent at the center of the cube

cubic arrangements: face centered cubic (fcc)

• has its constituents at the ends (corners) of a cube

• has an additional constituent at the center of the cube

• has an additional constituent at the center of each face of the cube

ionic crystal structures

• more complicated than those of metals

  • multiple constituents w/ diff sizes and charges

• generally ratio of cationic radius to the anionic radius determines the type of packing