Exam 2 Flashcards
Frequency
V
Wavelength
λ
Frequency measured in
hertz
Wavelength measured in
nm
Speed of light (on formula sheet)
C
3.00 * 108 m/s (
Energy and Frequency
Directly proportional
Energy and Wavelength
Inversely proportional
Wavelength and Frequency
Inversely Proportional
Energy of a photon equations (2 equations)
E= h * v (on formula sheet)
E= h*c/λ
E=J/Photon
What is h?
Planck’s constant
6.26*10-34J/s
(on formula sheet)
convert m to nm
convert m to um
1m= 1*109nm
1m=1*106um
ROYGBIV
Red low energy, longest wavelength. (infrared next to red)
Violet is highest energy, shortest wavelength. (UV next to violet)
ROYGBIV
Energy ——>
Frequency ——>
<————wavelength
Remember: Wavelength is inversely proportional!
Avagadros for light problems!
1 mol of photons/6.022*10^23 photons
Take something like #KJ/mol. Convert KJ to J then multiply by 1mol/6.022*1023photons so you get J/photon that can be used in E equations. E=hc/λ
Or if you have number of J/photon and want it in moles, multiply by 6.022*1023photons/1mole.
E=hc/λ
λ should be what unit?
METERS
q=mc∆T
c=4.184 J/gC heat capacity of water
m is mass in grams
Electron moving to a different energy level
only if it absorbs or emits a photon that has the same energy as the difference between the two energy levels
ground state
lowest energy oribtal n=1 for hydrogen
Excited State
When the electron is at a higher energy orbital n=2+ for hydrogen
Ionize
When an electron is ejected from an atom. Nfinal=infinity.
Losing an electron.
Exothermic and endothermic electrons
Electrons go from a high level (7) to a low level (2). ∆H= neg. Emission!
Endothermic go from low (2) to a high level (7). Absorption!
Lyman series
UV 90-100nm
ends at n=1
Balmer Series
400 to 700
Ends at n=2
Visible Light
IR series
IR 1000 nms
ends at n=3
all the series are exothermic BTW. High to low level.
Rydberg Equation Wavelength of electron transition in a Hydrogen atom
(all given on formula sheet)
1/λ =R(1/n12-n22)
n2>n1!!
R=1.097*107
Rydberg for energy transition (other one was to calculate wavelength)
RHC*Z2(1/nfinal2-1/ninitial2)
z=# of protons element has – so 1 for hydrogen.
RHC= -2.18*10-18
wavelength, mass, and speed– de broglie
λ =h/mu
mass in kg, u is speed in m/s and h is planck’s.
emissions at n=1
anything going or coming to n=1 has highest E. Passes through lots of levels. Or could use the rhc equation.
n
level (look at periodic table row).
Indicates relative distance
higher th enumber, greater the distance of the orbital from the nuclues, larger the shell, higher energy.
l
subshell
max value: of n-1. Max number of possible l values=n
Indicates shape
s, p, and d l values and shape
s =0; sphere
p=1; dumbbell
d=2; double dumbbell
f=3; flower
ml
-1 to +1 range.
Orientation.
labeling the slotsof the orbitals e.g. if p: -1, 0, 1 for the 3 slots.p l value is 1.
Pauli Exclusion principle
max number of e per orbital is 2
Hund’s rule
Fill with one e in each orbital, then go back and fill in the rest.
ms
-1/2 or +1/2
if up arrow, positive.
represents magnetic field
testing quantum validity
n>l> or equal to |ml|.
pauli exclusion principle
no 2 e in the same atom can have the same 4 quantum numbers.
2 e in an orbital must have opposing signs
aufbau principle
filling orbitals with the lowest energy
Z or nuclear charge
electrong is attracted to teh positive charge of the nucleus
Electron Shielding
If there are several electrons in the same orbital, they repel each other and shield one another from the attractive force of the nucleus (prevents feeling of full nuclear charge-Z). Experience an effective nucleuar charge (Zeff) due to shiledings. Effective shielding done by inner electrons loweres the effect of Zeff on outer electrons.
There is more shielding in the p orbital- easier to remove a p orbital electron.
electron removal order
remove from highest n first, then from f, d, p, s.
Inner/core electrons
noble gas electrons and any completed transition series (d10 or f14)
valence electrons equation for transition metals
number of electrons-core
para vs. diamagnetic
paramagnetic- unpaired
diamagnetic- all electrons are paired.
Transition orbital filling exceptions
most important: copper and chromium and palladium and silver
atomic size
left and down.
Zeff and shielding
zeff: up and right.
(more protons)
Shielding is the opposite. Down and left increases shielding.
ion size
look at what they are isoelectric with, compare the size of that.
If still tied,
Then, look at number of protons in the original ion to decide. (more protons, larger Zeff, smaller size, large Ionization energy)
Remember: cations (+) are smaller than anions (-).
Ionization energy trend
up and to the right increases IE (due to Zeff holding them tighter)
successive ionization energies
IE greatly increases when removing an inner (core) electron.
metal and nonmetallic character
think about location of metals and nonmetals on periodic table. Follow that trend.
covalents make acids or bases
acids
so acidity increases with nonmetallic character (up and right)
metals make acids or bases?
Bases and basciity increases as you go down and to the left on periodic table (with metal trend)
Redox behavior
Group 1 and 2 are losing electrons (LEO), oxidizing, so strong reducing agents.
Group 6 are gaining electrons, so strong oxidzing agents.
Electron Affinity
Energy released when an electron is added to a neutral gas atom. EA is -.
Increase in negativity as you go up and to the right.
1st Ea vs. 2nd EA
1st is exothermic and -, second is endothermic and a + ∆H
Lattice energy
energy absorved when 1 mol of an ionic compound breaks up into gas phase ions
What impacts lattice energy (strength of ionic bond)
1) ionic charge 2) ionic size
greater LE with greater charger
LE decreases as the ionic size increases
Look at anion size first. you want the smaller anion– greater LE
Steps of born haber cycle
sublimation, IE, bond dissociation, EA1, Lattic energy
sublimation
Li(s)—> Li(g)
+
IE1
Li(g)—>Li+ + e
+
bond dissociation
1/2 F2(g)—>F(g)
+
EA
F(g)+e—>F-1
-
lattice energy
Li+(g)+F1-(g)—> LiF(s)
-
Formation
∆H of f
Li(s)+1/2F2(g)—>LiF(s)
-
add up steps to get this
Electronegativity
up and to the right
ability to attract electrons.
Or drop by .5 going tot he left and 1/2 it going down.
H electronegativity
2.1
I electronegativity
2.5
Br electronegativity
2.8
Cl electronegativity
3.0
N electronegativity
3.0
O electronegativity
3.5
F electronegativity
4.0
Be and B and H
Be only needs 4 e in octet
B only 6
H 2
Formal charge
Valence electrons-dots-sticks
negative charge on most EN element, and positive on least EN.
Bond orders for resonance
single- 1
double- 2
resonance bond order= # of bonds/# of elements around central atom
what is the longest bond?
single bond
what is the weakest bond?
single bond
The shortest and strongest bond?
triple
Calculating ∆H from bond energies
Bonds broken (reactants)- bonds formed(products)
VSPER Shortcut
subtract highest multiple of 8— divide that by 8 to get the X
take the remainder from subtraction and divide by 2 to get lone pairs E.
2 groups
sp
linear
AX2
3 groups
Group: trigonal planar sp2
AX3-trigonal planar
AX2E1-bent
4 groups
tetrahedral-sp3
AX4-tetrahedral
AX3E1-trigonal pyramidal
AX2E2-Bent
5 groups
trigonal bipyramidal sp3d
AX5 trigonal bipyramidal
AX4E1-see saw
AX3E2- t shaped
AX2E3-linear
6 groups
sp3d2 Octahedral
AX6 octahedral
AX5E1 square pyramidal
AX4E2 square planar
bond angles for linear trigonal planar and tetrahedral
linear- 180
trigonal planar- 120
tetrahedral-109.5
small elements vs. large elements and bond size
small elements make short/strong bonds and large elements make long/weak bonds
most polar
greatest difference in electronegativity
most polar type of bond
ionic bond!
metal and nonmetal have biggest differences in EN.
molecular polarity test
is the geometry symmetric?
are the outer atoms the same?
symmetric molecular shapes
all the non E pair geometries and the Ax2E3 linear and the Ax4E2 square planar
multiple center compound polarity
- any lone pairs? automatically polar.
- Different configurations on central atoms makes it polar
- same configurations and same elements around it- nonpolar
sigma bond
single localized bond. produced by overlap of two s’s, 2 sp’s, or an sp with an s.
delocalize
sp orbital is created to delocalize the electron density around the central atom.
to move the electron density away from the middle of the lement- creates space for bonding and lowers energy of the element.
Pi bonds
double or triple localized.
overlap of 2 unhybridized p creates a pi bond and 4 p orbitals creates 2 pi bonds
These both have sigma bonds.
pi bonds weaker than sigma bonds
MO theory
delocalized. orbiatals are spread out, eliminates resonance and predicts stability.
MO theory bond order
1/2 (nonstars-stars)
bonding–antidbonding
bond order>0 the molecule forms and exists
greater mo theory bond order
greater the bond energy it has’more stable than separate atoms.
