Organic Chemistry Exam 1 Test Questions

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

 

?= dipole moment

 

e= magnitude of charge

 

d= distance between the charges

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

blue- most positive electrostatic potential
attracts negative charge

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

? is

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

?>?>?*>?*

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When 2 p AO form 2 MO, the AO of the more EN will contribute more to ______ while the least EN will for the _______
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more EN: bonding
lesser: antibonding
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VSEPR
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valence shell electron pair repulsion: minimization of e- repulsion by the positioning of lone pairs as far as possible
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what are the bond angles in methane, or any tetrahedron?
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109.5
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in organic chemistry, all single bonds are ____ bonds
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? bonds
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trigonal planar bond angle
what compound uses this?
answer

120
ethene (ethylene)
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what are in the different bonds in terms of ? and ??
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single: 1 ?
double: 1 ? and 1 ?
triple: 1 ? and 2 ?
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what is the strongest and shortest bond? why?
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triple; b/c its held together by 6 e-
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what is the angle for a triple bond?
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180

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