CHEM 241 Chapter 1 Part 2

tetrahedral

109.5

What is the approximate value of the bond angle A in the structure shown?

120

trigonal planar

120

linear

180

When interpreting skeletal structures of charged species, two general rules are useful. A charge on a carbon atom replaces _____ hydrogen atom(s), and the charge on any atom determines the number of covalent bonds and _____ electron pairs on that atom.

1; nonbonded

one lone pair

A carbon atom with a negative charge (and 3 bonds)

no lone pairs

A carbon atom with a positive charge (and 3 bonds)

Select all statements that correctly describe VSEPR theory.

A group is defined as an atom or a nonbonded (lone) pair of electrons. The most stable arrangement keeps electron pairs as far away from one another as possible.

Select all statements that correctly describe a π bond.

A multiple bond always contains at least one π bond. A π bond is formed by the side-by-side overlap of two p orbitals.

Which of the following statements correctly describe a nonpolar bond? (Select all that apply.)

A nonpolar bond is a bond in which the electrons are shared equally. A bond between two identical atoms is a nonpolar bond. Elements with very similar electronegativities form nonpolar bonds.

Which of the following statements correctly describe a polar covalent bond? (Select all that apply.)

A polar bond is said to have a dipole. A covalent bond is polar if the electronegativity difference between the two atoms is ≥0.5.

Select all the statements that correctly describe entacapone (which is used in the treatment of Parkinson's disease).

Atom 3 is sp2 hybridized. Entacapone has 14 carbon atoms Atom 2 has a lone pair that is delocalized.

L-Dopa is shown in the accompanying figure. Select all statements that describe this molecule.

Atom A has trigonal planar geometry. L-Dopa contains 11 hydrogen atoms. Atom A is sp2 hybridized. Atom C is sp2 hybridized.

Which of the following statements about CCl4 are true? (Select all that apply.)

CCl4 is a nonpolar molecule. The C-Cl bonds in CCl4 are polar.

Which of the following species are polar? (Select all that apply.)

CH2Cl2 CH3OH

Explain why CO2 is a nonpolar molecule.

CO2 is linear and therefore the individual bond dipoles cancel to give no net dipole.

Which of the following statements correctly describes the basic principle of VSEPR theory?

Each group around a central atom is located as far from the others as possible.

Which of the following options correctly describe electronegativity? (Select all that apply.)

Electronegativity is a relative quantity. Electronegativity measures the ability of an atom to attract electrons shared in a covalent bond.

Rank the following bonds in order of increasing bond length (shortest to longest), based on periodic trends, starting with the shortest bond at the top of the list.

H-F H-O H-S H-Se

Rank the following bonds in order of decreasing bond length, based on periodic trends, starting with the longest bond at the top of the list.

H-I H-Se H-Br H-S

Which of the following statements correctly describe hybrid orbitals? (Select all that apply.)

Hybrid orbitals are formed from the hybridization of atomic orbitals. The hybrid orbitals all have the same shape and energy. The type of hybrid orbital varies depending on the specific combination of atomic orbitals.

Which of the following options correctly describe the steps used to determine the polarity of a molecule? (Select all that apply.)

Individual bonds are classified as polar or nonpolar based on electronegativity differences. If a molecule contains no dipole moments across any bonds it will be nonpolar. The molecular geometry must be determined before one can decide whether or not individual bond dipoles cancel.

Which of the following statements correctly defines hybrid orbitals?

Orbitals used for bonding that are formed by "mixing" atomic orbitals from the same atom

Head of an arrow

Pointing toward the more electronegative element

Tail of an arrow with a perpendicular line drawn through it

Positioned at the least electronegative element

δ+

Positioned on the most electron deficient atom

δ-

Positioned on the most electron rich atom

Which of the following is NOT a correct representation of a tetrahedral system?

Structure A

Select the structure in which the polarity of the bond has been marked incorrectly.

Structure II

Which of the following statements correctly describe the bonding in the structure shown? (Select all that apply.)

The bond between O and C is formed by the overlap of an sp3 orbital from each atom. The O lone pairs are both in sp3 orbitals.

Which of the following statements correctly describe a C-F bond? (Select all that apply.)

The bond dipole should point towards F. Carbon should be marked with a δ+ symbol.

Which of the following defines the ground state of an atom?

The lowest energy state of an atom, where all electrons are in the lowest energy levels possible

What determines the number of atomic orbitals that must be hybridized to form the hybrid orbitals for a given atom?

The number of groups around a given atom

Which of the following correctly describes the geometry and shape around the nitrogen atom in the molecule shown?

The shape around the nitrogen is trigonal pyramidal. The geometry around the nitrogen is tetrahedral.

True or false: When using VSEPR theory to determine molecular geometry, double and triple bonds count as a single group even though they consist of 2 and 3 electron pairs respectively.

True

Which of the following options correctly describe the conventions used to represent a tetrahedral arrangement of atoms on a flat plane? Select all statements that apply.

Wedges and dashes are used to represent groups that are aligned one behind another. Solid lines are used to represent any bonds in the plane of the page. There will always be one dashed line and one wedged line in the drawing. There will always be two solid lines showing bonds to the central atom.

solid line

a bond in the plane

A bond dipole can be indicated with a(n) ____ that points toward the most electronegative element. The separation of charge can also be depicted with delta positive and delta ____ signs to indicate the unequal sharing of electron density.

arrow negative

Which of the following contribute to the observed geometry around a given atom?

bond angle bond length

As the number of shared electrons between two nuclei increases, the bond length _____ and the bond strength _____.

decreases, increases

Electronegativity decreases

down a column.

Correctly order the steps necessary to determine the geometry around a given atom. Place the first step at the top of the list and the last step at the bottom of the list.

draw a valid count groups match the number

The measure of an atom's attraction for the electrons in a covalent bond is termed ______.

electronegativity

The number of hybrid orbitals formed from the hybridization of atomic orbitals is _____ the number of orbitals mixed, each having _____ and energy.

equal to; the same shape

An atom is in its lowest energy state, or _____ state, when its electrons are in the lowest possible energy levels. If an electron moves to a higher energy state the atom is said to be in a(n) _____ state.

grounded, excited

The mathematical process of mixing atomic orbitals from a specific atom is called the _____ of orbitals and the new atomic orbitals formed are referred to as _____ orbitals.

hybridization; hybrid

Arrange the steps to determine overall molecular polarity in the correct order. Place the first step in the procedure at the top of the list and the last step at the bottom of the list.

identify determine

The structure shown represents an atom surrounded by 4 bonds drawn using the wedge-dash format. The bond marked "a" is a bond _____ the plane, the bond marked "b" is _____ the plane, and the bond marked "c" is _____ the plane.

in, in front of, behind

When drawing a condensed structure of an organic compound, multiple bond lines are usually ______ while single bond lines are often ______.

included, omitted

Electronegativity values ______ from left to right across a row and ______ down a column of the periodic table.

increase, decrease

The average distance between the centers of two bonded nuclei is called the bond

length

The shape of a given molecule is determined by bond _____ and bond _____.

length; angle

A covalent bond in which the electrons are shared unequally is called a

polar dipole

If the geometry of a molecule is such that the individual dipoles _____ each other the molecule will be polar. Conversely, if the geometry of the molecule is such that the individual dipoles _____ each other the molecule will be nonpolar.

reinforce, cancel

A C-H bond formed between an sp carbon orbital and the 1s orbital of H will have a _____ bond length and _____ bond strength compared to a C-H bond formed between an sp3 carbon orbital and the 1s orbital of H.

shorter, greater

A bond that concentrates electron density on the axis that joins the two nuclei is called a(n) _____ bond.

sigma

Triple bonds contain only one ____ bond

sigma

What is the hybridization of the two carbon atoms in the structure shown (from left to right)?

sp2, sp

In the structure shown, the nitrogen atom is _____ hybridized and its lone pair resides in a(n) _____ orbital.

sp2, sp2

Consider the labeled atoms in the structure shown. The C of the CH3 group is ____hybridized while the C of the triple bond is___ hybridized

sp3 sp

C of CH3 groups

tetrahedral

central C atom

trigonal planar

What is the shape of a molecule where the central atom has tetrahedral electron geometry with one lone pair?

trigonal pyramidal

Rank the following bonds from the shortest to the longest. Place the shortest bond at the top of the list and the longest bond at the bottom of the list.

triple double single

A double bond contains _____ electron pair(s), and in VSEPR theory a double bond is considered to be _____ group(s).

two, one

The hybridization of one s and one p orbital will result in the formation of _____ sp hybrid orbitals. This will leave _____ unhybridized p orbital(s), which is/are at right angles to the hybrid orbitals. The formation of a group of sp2 hybrid orbitals leaves _____ unhybridized p orbital(s).

two; two; one

A bond formed by the side-by-side overlap of two p orbitals is called a _____ bond. This type of bond is weaker and more reactive than a _____ bond.

π, σ

O atom

Choice bent

C of CH3 groups

Choice tetrahedral

sp3

25

The charged oxygen atom in the structure shown has ____ lone pairs of electrons, which have not been included.

3

sp2

33

An sp2 hybrid orbital has _____ % s character and _____ % p character.

33; 67

sp

50

Which of the following statements correctly describe a σ bond? (Select all that apply.)

A σ bond is cylindrically symmetrical. All single bonds are σ bonds.

Which of the following statements correctly describe the conventions used when drawing a skeletal structure for an organic compound? (Select all that apply.)

All heteroatoms are drawn and the hydrogens directly bonded to them. The unlabeled end of a line represents a C atom. It is assumed that every carbon atom has enough hydrogens to make it tetravalent.

Which of the following statements correctly describe the hybridization of a given atom surrounded by a given number of groups? (Select all that apply.)

An atom surrounded by two groups will be sp hybridized (two hybrid orbitals). An atom surrounded by three groups will be sp2 hybridized (three hybrid orbitals).

three lone pairs

An oxygen atom with a negative charge (and one bond)

The bond lengths (in pm) for several different C-H bonds are provided in the table shown. Which of the following statements correctly explains this trend?

An sp3 orbital has the least amount of s character and therefore makes the weakest, longest bond.

Which of the following statements correctly describe the approximate bond angles for the molecule in the diagram?

Angle A is 180° Angle B is 120°

Which of the following defines bond length?

Average distance between the centers of two bonded nuclei

Which of the following steps are necessary to determine the geometry around a given atom?

Count the number of groups around a given atom. Draw a valid Lewis structure. Match the number of groups with the associated geometry.

Which of the following statements correctly describe the conventions used when drawing condensed structures in organic chemistry? (Select all that apply.)

Lone pairs are omitted Atoms are drawn next to the atoms to which they are bonded

Select all statements that correctly describe the composition of a carbon-carbon triple bond.

The σ bond is formed by the overlap of sp orbitals. The π bonds in a triple bond are in perpendicular planes relative to one another.

True or false: A molecule can be nonpolar despite containing polar bonds.

True

dashed line

a bond behind the plane

wedge

a bond in front of the plane

In the skeletal structure for an organic compound, it is assumed that there is a ____ atom at the end of any line and at the junction of any two lines. This type of structure omits all ____ atoms except those directly bonded to a heteroatom.

carbon hydrogen

Nonpolar molecules

contain no polar bonds, or two or more bond dipoles that cancel.

Polar molecules

contain one polar bond, or two or more bond dipoles that reinforce each other.

Electronegativity increases

from left to right across a row.

The number of ____ around a given atom corresponds to the number of ____ orbitals that must be hybridized to form the hybrid orbitals.

groups atomic

A bond between two atoms of identical or similar electronegativity is a _____.

nonpolar covalent bond

Structure c

one H atom, no lone pairs

Structure d

one H atom, one lone pair