Exam 3 Flashcards
how are discrete line spectras produced
exciting a gas at a low partial pressure
formula for energy absorbed/emitted
hc/wavelength
quantized definition
a system is limited to specific energy values
when is a photon emitted
when an e- transitions from a ground state to an excited state
energy of a photon formula
h * v
relationship between electron energy and distance from nucleus
as one increases, so does the other
what is coulomb’s potential?
attractive force between a positive nucleus and an electron
important features of all orbital models
energies of electrons are quantized
electron energy increases with distance from nucleus
discrete energies (lines) in spectra come from quantized electronic energies
constructive intereference
peaks and troughs coincide to amplify
destructive interference
peaks and troughs conflict, cancels out
how to obtain probability density
square the wavefunction
principle quantum number
n
location of energy level/shell number
angular momentum quantum number
l
defines shape of orbital
any value from o to n-1
magnetic quantum number
m1
defines z component of l
ex. l = 1, m1 = -1, 0, +1
is absorption/emission of light endo or exothermic?
absorption: endothermic
emission: exothermic
wavefunction squaured …
probability of finding an electron at a given point near the position
radial distribution
total probability of finding an electron at a given distance (r) from the nucleus
- r increases with surface area
describe the electron density graph of the 1s orbital
starts high, goes lower, no nodes
describe the electron density graph of the 2s orbital
starts high, one node, one peak
describe the electron density graph of the 3s orbital
starts high, 2 nodes, one large peak, one smaller peak
describe the radial distribution graph of the 1s orbital
starts low, not at zero, one massive peak
describe the radial distribution graph of the 2s orbital
starts low, closer to zero, one node, two peaks second is larger than the first
describe the radial distribution graph of the 3s orbital
starts low, closer to zero, two nodes, three peaks getting progressively larger
orbitals in the nth energy level
n^2
electrons in the nth energy level
2n^2
orbitals in the l-subshell
2l + 1
how many electrons can each orbital hold
2
what is the pauli exclusion principle
no two e- can have the same set of 4 quantum numbers
what l values correlate to subshells?
l = 0, s
l = 1, p
l = 2, d
l = 3, f
difference between surface nodes and radial nodes
surface nodes (planar) are found at the original of the radial graphs, while radial nodes are not
total nodes (surface + radial) =
n - 1
surface/planar nodes =
l
diamagnetic definition
all e- are paired
paramagnetic definition
at least one unpaired e-
isoelectronic definition
same #e-
isovalent definition
same #valence e-
what are degenerate orbitals
having the same energy
what is effective nuclear charge
Zeff
- strength of the e- – nucleus interaction
- = Z (atomic number) - # core e-
- increases from left to right
- increases as electron subshell level decreases
what are the common periodic table trends
- atomic radii (size) increases from right to left and down
- ionization energy (to remove an e- from a gaseous atom) increases left to right and up
- electron affinity (energy change with addition of an e- to a neutral gas) more negative left to right and up
- ionic radii –> anions are larger than cations
definition of electronegativity
the degree to which an atom can attract an e- in a bond
nonpolar covalent bond
equal sharing of e- between two identical nonmetal elements
polar covalent
unequal sharing of e- between two nonmetals
small electronegativity difference
ionic
metal + nonmetal
e- are transferred to nonmetal
large electronegativity difference
as electronegativity increases, what happens to the following?
- bond polarity
- ionic character
- covalent character
- increase
- increase
- decrease
what is bond order
essentially, number of bonds
= # bonds/ # bond locations
as bond order increases, what happens to the following?
- bond strength
- bond length
- bond dissociation energy
- increase
- decrease
- increase
what is formal charge
charge on an atom as determined by lewis dot structure
= #valence e- - #e- shown around atom in lewis dot structure
what is needed for a lewis dot structure to contribute most in resonance?
- smaller (ideally 0) formal charges
- more zeros for formal charges
- if formal charges are equal, the structure with the more negative formal charge on the more electronegative atom
electron pair geometry versus molecular geometry
EPG:
- geometry including all domains (including lone pairs)
MG:
- refers to actual arrangement of atoms
- does not include lone pairs
what is a dipole moment? when does it cancel?
dipole moment: measure of molecular polarity
- cancels when bond vectors cancel out –> nonpolar molecule
- when bond vectors create a net vector –> polar molecule
relate VSEPR and polarity
(#atoms, #lone pairs)
POLAR: (2,1) (3,1) (2,2) (4,1) (3,2) (5,1)
NONPOLAR: (2,0) (3,0) (4,0) (5,0) (2,3) (6,0) (4,2) AND all atoms around central atom are the same
are hydrocarbons polar or nonpolar?
nonpolar
are binary atom molecules polar or nonpolar?
nonpolar
are X-Y molecules polar or nonpolar?
polar
where do sigma bonds lie
directly between the two nuclei of atoms
what type of bond is in all single, double, or triple bond?
sigma
compare sigma bonds and pi bonds
SIGMA
- can rotate
- symmetrical
- stronger
PI
- cannot rotate
- weaker
where do pi bonds lie
above and below the internuclear axis
what is required to make a pi bond?
two p-atomic orbitals
