(Exam 2 - Harrison CHEM 27 material): C-14 Hybrid Knewton Alta
The double bond in H2C = CH2 consists of ______ sigma bond(s) and ______ pi bond(s).
1 ; 1
The hybrid orbitals have shapes/orientations that are _______ those of the isolated atoms' atomic orbitals.
different from Explanation: When atoms are bonded in a molecule, their individual wave functions are combined. These hybrid orbitals are new orbitals that have new geometry compared to the individual atoms' atomic orbitals.
A sigma bond involves:
direct orbital overlap
Which type of orbital overlap results in the strongest covalent bond?
direct overlap
On a diagram showing the potential energy of two hydrogen atoms according to their internuclear distance, the lowest point will correspond to the:
ideal bond length Explanation: The lowest energy will be the ideal bond length. This length is the distance between the nuclei that maximizes the electrostatic attraction between the two electrons and the two nuclei but minimizes the proton-proton repulsion.
The optimum distance between two bonded nuclei is when the energy is:
lowest
Which geometry corresponds with an sp^3d^2 hybrid orbital? 1) trigonal planar 2) octahedral 3) trigonal bipyramidal 4) tetrahedral
octahedral
In a sigma bond, the electron density is concentrated:
on the internuclear axis itself
A triple bond always consists of: _____ sigma bonds and ______ pi bonds
one sigma bond and two pi bonds
How many sigma and pi bonds are in a triple bond?
one sigma bond and two pi bonds
In order for a pi bond to form, there must be: 1) overlap of s orbitals 2) overlap of unhybridized orbitals 3) overlap of hybrid orbitals 4) hybrid orbitals with different energies
overlap of unhybridized orbitals
A _____ bond is a covalent bond where the regions of orbital overlap are above and below the internuclear axis.
pi ; form p orbitals
A "node" is a characteristic in which of the following? 1) delta bond 2) sigma bond 3) pi bond 4) gamma bond
pi bond ; In pi bonds, the orbitals overlap parallel to the internuclear axis, so along the axis itself a node forms (where there is no probablity of finding an electron).
Unhybridized orbitals overlap to form:
pi bonds
A pi bond involves:
side-by-side, or lateral orbital overlap with the electron density concentrated on opposite sides of the internuclear axis.
A _______ bond is a covalent bond where the electron density is concentrated in the region along the internuclear axis.
sigma
Direct overlap of hybrid orbitals yields a ____________ bond, and lateral overlap of unhybridized orbitals yields a ____________ bond.
sigma, pi
What is the hybridization of carbon in carbon dioxide (CO2)?
sp
What is the hybridization of boron in boron trichloride (BCl3)? 1) sp^3 2) sp^2 3) sp
sp^2
What is the hybridization of the oxygen atom in a water molecule?
sp^3
What type of hybridization is commonly associated with tetrahedral geometry?
sp^3
Which of the following determines the strength of a covalent bond? 1) the charges of the ions involved 2) the amount of overlap for the orbitals involved 3) the mass of the atoms involved 4) all of the above
the amount of overlap for the orbitals involved
Hybridization was developed to explain observations about:
the bond angles in certain molecules Explanation: From valence bond theory, bond angles in a molecule like water would be expected to be 90 degrees rather than the observed 104.5 degrees, so hybridization was developed to understand these observations.
We can predict the number of bonds an atom can form by counting: (select all that apply) 1) the number of core electrons needed to form an octet 2) the number of valence electrons 3) the number of additional electrons needed to form an octet 4) The total number of core electrons.
the number of additional electrons needed to form an octet AND the number of valence electrons
Which bond is strongest in a carbon-carbon triple bond? 1) the sigma bond 2) the first pi bond 3) the second pi bond 4) these are all the same strength
the sigma bond; involved in direct orbital overlap
Which of the following describes a covalent bond as the overlap of half-filled atomic orbitals that yields a pair of electrons shared between two bonded atoms? 1) atomic orbital theory 2) covalent bond theory 3) electron pair theory 4) valence bond theory
valence bond theory
What statement is NOT correct about sigma bonding? 1) Rotation around single sigma bonds does not occur easily. 2) The end-to-end orbital overlap does not depend on the relative orientation of the orbitals on each atom in the sigma bond. 3) The bonding electron density of sigma bonding orbitals is symmetric about the axis. 4) Hybrid orbitals on carbon are used to form the sigma bonds between carbon atoms and between carbon and hydrogen atoms.
1) Rotation around single sigma bonds does not occur easily. Explanation: Rotation around single sigma ) bonds occurs easily because the end-to-end orbital overlap does not depend on the relative orientation of the orbitals on each atom in the bond. Rotation around the internuclear axis does not change the extent to which the bonding orbitals overlap because the bonding electron density is symmetric about the axis. Hybrid orbitals on carbon are used to form the sigma-bonds between carbon atoms and between carbon and hydrogen atoms.
Which of the following create sigma bonds? 1) overlap of two s orbitals 2) end-to-end overlap of two p-orbitals 3) side-by-side overlap of two p-orbitals 4) overlap of an s orbital and a p orbital
1) overlap of two s orbitals 2) end-to-end overlap of two p-orbitals 4) overlap of an s orbital and a p orbital NO THREE: side-by-side overlap of two p-orbitals
A hybridized atomic orbital can contain or participate in which of the following? 1) sigma bonds 2) lone pairs of electrons 3) single unpaired electrons (radicals) 4) pi bonds
1) sigma bonds 2) lone pairs of electrons 3) single unpaired electrons (radicals)
How many unhybridized p orbitals are there around the central atom of beryllium chloride, BeCl2?
2 Explanation: There are 2 regions of electron density surrounding the central beryllium atom, which will arrange themselves in a linear geometry. Beryllium must be sp hybridized, and so there must be 2 unhybridized p orbitals in BeCl2 What is the hybridization of oxygen in water
How many sigma and pi bonds are in CO2?
2 sigma, 2 pi bonds
Which of the following is the most likely bond angle in a molecule where the central atom is sp hybridized? 1) 109.5 degrees 2) 180 degrees 3) 120 degrees 4) 90 degrees
2) 180 degrees
Which of the following statements about hybridization are true? 1) Hybrid orbitals exist in isolated atoms. 2) Hybrid orbitals within the same atom have the same energy and shape. 3) Hybrid orbitals are described mathematically as a linear combination of atomic orbitals. 4) An atom can have both hybridized and unhybridized orbitals at the same time.
2) Hybrid orbitals within the same atom have the same energy and shape. 3) Hybrid orbitals are described mathematically as a linear combination of atomic orbitals. 4) An atom can have both hybridized and unhybridized orbitals at the same time.
Which molecule has a central atom that is sp^3d^2 hybridized? 1 ) XeF2 2) XeF4 3) XeF6 4) none of the above
2) XeF4
A pi bond involves: *select all that apply 1) direct orbital overlap 2) lateral orbital overlap 3) a node 4) none of the above
2) lateral orbital overlap AND 3) a node
Which is the following is the most likely bond angle in a molecule where the central atom is sp^2 hybridized? 1) 109.5 degrees 2) 180 degrees 3) 120 degrees 4) 90 degrees
3) 120 degrees
What is the hybridization of oxygen in water (H2O)? 1) sp 2) sp^2 3) sp^3
3) sp^3
Four atomic orbitals will combine to give how many hybrid orbitals?
4 hybrid orbitals
Sigma bonds can occur between: 1) two s orbitals 2) two p orbitals (end-to-end) 3) an s orbital and a p orbital 4) all of the above
4) all of the above
How many sigma (σ) and pi (π) bonds are there in the ethene (C2H4) (neutral charge)
5 sigma bonds, 1 pi bond
What type of bond is formed by the direct overlap of hybrid orbitals?
A sigma bond; direct = sigma, lateral = pi
Which of the following must occur for a covalent bond to result? 1) The single electrons in each orbital combine to form an electron pair. 2) An orbital on one atom overlaps an orbital on a second atom. 3) Both A and B 4) Neither A or B
Both A and B
Which bond is the shortest? 1) F-F 2) Cl-Cl 3) I-I 4) Br-Br
F-F ; smaller atom size = shorter bonds
Which molecule has a central atom that is sp^3d^2 hybridized? 1) ClF3 2) SF4 3) PCl5 4) IF5
IF5
Which of the following has the correct number of s, p, and d orbitals to describe an octahedral arrangement? 1) 3 s, 1 p, 2 d 2) 2 s, 1 p, 3 d 3) 0 s, 3 p, 3 d 4) none of the above
None of the above Explanation: The octahedral arrangement has one s, three p, and two d orbitals. The octahedral arrangement has six electron dense regions and is not possible for atoms in the first or second period of the periodic table.
Which of the following will be the strongest bond? 1) a direct overlap with a lot of overlapping space 2) an angled overlap with a lot of overlapping space 3) a direct overlap without a lot of overlapping space 4) an angled overlap without a lot of overlapping space
a direct overlap with a lot of overlapping space
What forms when two pairs of electrons are shared between a pair of atoms?
a double bond
A plane with no probability of finding an electron is known as:
a node
In a pi bond, what can be found along the internuclear axis?
a node
Which kind of orbitals can s orbitals overlap with? 1) sp 2) sp^2 3) sp^3 4) all of the above
all of the above
Which of the following produces sigma bonds? 1) the overlap of an s and p orbital 2) the overlap of two s orbitals 3) the end-to-end overlap of two p - orbitals 4) all of the above
all of the above
Which bond is the shortest? 1) carbon-oxygen single bond 2) carbon-oxygen double bond 3) carbon-oxygen triple bond 4) these are all the same length
carbon-oxygen triple bond ; adding bond --> bond length contracts
Greater atomic orbital overlap _______________ bond length and ________________ bond strength.
decreases, increases
