Chp. 8, 9, 10

What are the 3 Electrostatic interactions of Covalent Bonding?
1. attractions between electrons & nuclei
2. repulsions between electrons
3. repulsions between nucleus
What is Electronegativity?
The ability of an atom in a molecule to attract electrons to itself.
*greater electronegativity= greater ability to attract electrons
*measures how strongly the atom holds on too electrons, also related to ionization energy & electron affinity
What are polar covalent bonds and what are non polar covalent bonds?
-polar covalent: sharing electrons unequally,
-non polar covalent: sharing electrons equally
What is the change in Electronegativity for a polar covalent bond? Ionic bond? Nonpolar Covalent?
-Non polar: 0.0-0.4
-Polar Covalent: 0.5-1.9
-Ionic: 2.0 or greater
What type of bond does HCl has?
H electronegativity: 2.1
Cl electronegativity: 3.0
3.0-2.1= .9 ( always big-small)
This is a polar covalent bond
What happens when electrons are unshared equally?
It becomes a polar covalent bond, & a bond dipole results. This only happens when you have a polar covalent bond & the arrow goes toward the atom with the greater electronegativity value
When drawing a Lewis Dot Structure what is usually the Central Atom?
It is usually the least electronegative element
If you don’t have enough electrons for your Lewis Dot structure what do you do with them?
Make double bonds
If you have extra electrons where do they go?
They go on the central Atom
What are some exceptions to the Octect rule?
– Be wants 4 electrons (wants 2 bonds)
– Elements in IIIA (mainly Boron) want 3 bonds, 6 electrons
– Compounds such as S, P, As, & I can sometimes violate Octect rule, can add more electrons
What is something special about central atoms with expanded Octets?
– Any element with an energy level = to or > than 3 can have an expanded octet. Electrons can reside there since they because they are in the d subshell
What is the formula to calculate formal charge?
formal charge=group number-(number of bonds + number of unshared electrons)
– the FC of all the atoms must sum to 0 in molecules
How do you know you have resonance in a molecule?
– you have resonance within a molecule when you can make a double bond in 2 places
What is bond enthalpy?
– Bond enthalpy or bond energy is the energy needed to break one mole of bonds in a gaseous covalent substance to form products in the gaseous state at constant temp and pressure
A) If the change in Heat in the Rxn is negative what type of reaction is that?
B) If the change in Heat in the Rxn is positive what type of reaction is that?
A) exothermic (releases heat)
B) endothermic (absorbs heat)
-Which bond is stronger? double bond or single bond?
Double bond
Out of a sigma bond and a pi bond which one is stronger?
sigma bonds are stronger than pi bonds
What type of bond do you have when it is single?
You have a sigma bond
what type of bond do you have when you have a double bond?
you have one sigma bond and the other is a pi bond
what types of bonds do you have when you have a triple bond?
you have one sigma bond and 2 pi bonds
Boyle’s Law
-T & n are constant & pressure and volume are inversely related
– if pressure increases then volume decreases
Charles Law
– Temp of a gas is directly related to Volume, P & n are constant
– when temp inc, volume inc
– Gay Lussac’s Law
– pressure & temp directly related
– V & n are constant, so when pressure inc. temp also inc
Effusion:
– The escape of gas molecules through a throughout a tiny hole into an evacuated space
Diffusion:
-is the spread of one substance throughout a space or through out a second substance
What were the two assumptions that were made about the Kinetic Molecular theory break down?
– attraction between gas molecules are negligible
– volume of gas is negligible to volume of container
Do real gases have finite volumes?
– The unoccupied space where gas molecules can move is less than the volume of the container
-gas volumes are slightly greater than predicted
Are real gases attracted to one another?
Yes, the impact against the wall of the container is lessened & pressure is less than assumed for an ideal gas
What is the Van der Waals Equation?
(P-n^2a/v^2)(V-nb)=nRT
What is the Ideal Gas law equation?
PV=nRT