Organic Chemistry Exam 1

where is carbon located in the periodic table?
2nd row
atoms to the left of carbon tend to
give up electrons
atoms to the right of carbon tend to
receive electrons
what prevents the positively charged nucleus from drawing in the negative electrons?
kinetic energy of the electrons
where does the mass of an atoms mostly come from? the volume?
mass-protons and neutrons=nucleus
volume-electrons
atomic number
number of protons in a nucleus OR number of electrons on a neutral atom
mass number
number of protons and neutrons
isotopes
have the same atomic numbers BUT different mass numbers because they have a different number of neutrons
half-life
time it takes for 1/2 of the nuclei to decay
atomic weight
average weighted mass of an element’s atoms
molecular weight
sum of atomic weights of all the atoms in a molecule
wave equation
describes the behavior of an electron
wave function or orbital
is the solution to a wave equation and tells
1. energy of electron
2.where it is most likely to be found
quantum mechanics
characterizes movement of an electron around the nucleus like the wave motion of a guitar string
atomic orbital
3-D region of volume where an e- is most likely to be found
the closer an atomic orbital is to the nucleus, the _______ it’s energy
lower
degenerate orbitals
orbitals with the same energy
what are the 3 principles that are considered in ground state electron configurations?
1. aufbau
2. pauli-exclusion
3. hund’s rule
aufbau principle
an electron would rather occupy an available atomic orbital of the least energy (closer to the nucleus)
pauli-exclusion principle
1. max of 2 e- in each atomic orbital
2. they must be of opposite spin
hund’s rule
an e- would rather occupy an empty atomic orbital before one that already has an e- to minimize electron repulsion
electropositive
where are they found?
elements that readily lose an e- and become + charged; 1st column: the alkali metals
electronegative
elements that will readily gain an electron and become positive; column 17
ionic bond
bond due to only electrostatic attractions (attraction b/t opposite charges) and where electrons are transferred and NOT shared
if a hydrogen atom loses its only e- then it becomes
positive ion: a proton
if a hydrogen atom gains an e- to have 2 electrons in its outer shell it is a
negatively charged ion: a hydride ion
nonpolar covalent bond
electrons are shared equally
polar covalent bond
the atoms of the bond have different electronegativities,therefore the e- are NOT shared equally
the greater the difference of the electronegativity in a polar bond the more ___________ the bond is
polar
what type of bond has a dipole?
a polar bond
dipole
a polar bond that has a – and + end
dipole moment
the size of the dipole in a polar bond
what is the formula used to determine the dipole moment?

?=e x d

 

?= dipole moment

 

e= magnitude of charge

 

d= distance between the charges

what is the charge on an electron in electrostatic units (esu)?
4.8 x 10-10 esu
a bond length of 1.39A would be what value in cm?
1.39 x 10-8 cm
6.97 esu cm or 6.97 x 10-18 esu cm would be what value in D (debye) units?
6.97 D
electrostatic potential maps
show the distribution of charge in a molecule
in an electrostatic map what does blue and red represent? what is most attracted to them?
red- most negative electrostatic potential: attracts + charge

blue- most positive electrostatic potential
attracts negative charge

why in the electrostatic potential maps for LiH and HF was the H in LiH larger?
Because a potential map marks the edges of a molecule’s electron cloud and the electron cloud around the H in LiH is largest because it has more electrons around it than the other H in HF.
Lewis structure
uses dots to represent valence electrons
formal charge
FC=valence electrons – (lone pair electrons + 1/2 bonding electrons)
free radical or radical
any species with a single lone pair electron
kekule structures
lone pair e- are not shown except to make a point
in a neutral atom how many lone pairs should these atoms ALWAYS have?
nitrogen-
oxygen-
halogen (such as chlorine)-
N-1
O-2
Halogen-3
condensed structures
don’t show covalent bonds and list atoms bonded together
Heisenberg uncertainty principle
cannot determine location and momentum of an electron simultaneously
is the electron density more or less in 2s than in 1s?
the e- density in 2s is less because it is a larger sphere that is farther away from the nucleus
radial node
node found in spherical atomic orbital (s), probability of finding a e- is 0
nodal plane
node of the p orbital
molecular orbital theory (MO)
covalent bonds form when AO combine to form MO
? bond
formed when two “s” orbitals overlap or two “p” orbitals overlap end on end
? bond
formed when two “p” atomic orbitals overlap side to side
which bonds are cylindrically symmetrical? which aren’t?

? is NOT

? is

maximum stability=
minimal energy
bond length
when maximum stability is achieved (which means minimal energy)
bond dissociation energy
energy needed to break a bond or energy that is released when the bond forms
when a covalent bond is formed, what happens in terms of energy?
energy is released when a covalent bond is formed
explain ? bonding
is constructive; e- are most likely in between nuclei, attracting them and increasing e- density which binds atoms
explain ?* bonding
destructive, there is a node so no e- will be there. the two + nuclei will repel each other
how does the amount of overlap affect the strength of a bond?
the greater the overlap=stronger covalent bond
the strongest covalent bonds are formed by e- that occupy MO with the ______ energy. Why?
least; because the lower the energy, the more stable
how many nodes do these have (for s and p)?
?
?
?*
?*
?- s:0 p:2
?- p:1
?*- s:1 p:3
?*- p:2
in terms of overlap, which is greater: p orbitals overlapping side to side or end to end?
end to end
which is more stronger?
?
?
?*
?*
place them in order
a ? is stronger than ? because it is more stable (less energy).

?>?>?*>?*

When 2 p AO form 2 MO, the AO of the more EN will contribute more to ______ while the least EN will for the _______
more EN: bonding
lesser: antibonding
VSEPR
valence shell electron pair repulsion: minimization of e- repulsion by the positioning of lone pairs as far as possible
what are the bond angles in methane, or any tetrahedron?
109.5
in organic chemistry, all single bonds are ____ bonds
? bonds
trigonal planar bond angle
what compound uses this?
120
ethene (ethylene)
what are in the different bonds in terms of ? and ??
single: 1 ?
double: 1 ? and 1 ?
triple: 1 ? and 2 ?
what is the strongest and shortest bond? why?
triple; b/c its held together by 6 e-
what is the angle for a triple bond?
180
x

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