network solids Flashcards
network solid examples
C (diamond), SiC (s), SiO2 (quartz)
isoelectric
same number of electrons as nearest noble gas
boron has an unfulfilled octet
happy with 6 valence electrons, forms more reactive and less stable bonds
why does sulfur form an expanded octet
it uses a nearby d sub shell which allows for more room in its valence shells, expanded octets occur during 2p and beyond
resonance structures
same formula, different lewis structures
what is polarizability
tendency of an electron cloud to distort,
The larger the atomic or molecular polarizability, the greater the induced dipole moments, leading to stronger intermolecular forces and thus higher surface area interactions.
Why is Bromine a liquid at room temperature
more electrons, more polarizable which means its bonds are harder to break preventing it from changing states
why would the halogens have an increased melting and boiling point than the noble gases
because the halogens are diatomic
what makes dissociation possible
ion-dipole forces
properties of network covalent bonding
- hardness
- melting point
- solubility: insoluble in solvent because they are so large
NO INTERMOLECULAR FORCES IN NETWORK COVALENT BONDS
viscosity
resistance of liquid to flow
increased viscosity with increased imf and decreased temperature
- larger molecule increases ldf strength and decreases the sliding around
surface tension
h2o acts as if it has a “Skin” on it due to inward forces on surface, caused by hydrogen bonding
cohesion and adhesion:
intermolecular forces that bind to similar molecules of one another are cohesive forces
intermolecular forces that bind a substance to a surface- adhesive
what produce capillary action
adhesive forces, pulls h2o up a tube
capillary action
- adhesive forces attract the liquid to the wall of the tube
- cohesive forces attract the liquid to itself
- h2o has stronger adhesive forces with glass whereas mercury has stronger cohesive forces with itself
concave surface
- adhesive outweighs cohesive, where water molecules adhere to glass more than themselves
convex surface
- cohesive outweighs adhesive, where mercury molecules collide with each other more than adhering to the wall
phase changes
energy is either added or released
endothermic= adding temperature to break bonds, energy is absorbed, increased potential energy
exothermic= lowering temperature, releasing energy causing new bonds to form, decreased potential energy
example of a phase change
- sweat pulls energy in the form of heat from your body as water (sweat) evaporates to make you feel cooler
heat of fusion
heat of vapourization
heat of sublimation
fusion: energy required to change a solid at its melting point to a liquid
vapourization: energy requried to change a liquid at its boiling point to a gas
sublimation: energy required to change a solid directly to a gas
melting point=
freezing point
product of mass and heat of fusion
= heat
emission spectrum
When an electric current passes through a gas, it gives energy to the gas. This energy is then given out as light of several definite wavelengths (colours).
valence bond theory: how chemical bonds are formed by the overlap of orbitals
As they move closer and closer together, orbital overlap begins to occur, and a bond begins to form.
