Chemistry chapter 8

What determines an elements physical and chemical characteristics

The composition and internal arrangement

T or F Lewis structures leave out valuable information about the compounds they represent (because they are 2D structures of 3D molecules)

True

The two models for bonds

Valence bond theory; molecular orbital theory

The theory that states how the shared electrons of covalent bonds occupy partially filled valence orbital regions that overlap between bonded atoms. Two bonding orbitals are superimposed (the overlapping space becomes available to both nuclei) both atoms acquire another valence electron that fills the vacancy in that particular orbital

Valence bond theory

Valence bond theory is also called

localized electron theory

T OR F in the valence electron theory, no single theory of bonding accounts for everything that chemists observe about covalent bonds

True

Theory in which S orbitals overlap, S and P orbital overlap, then P orbitals overlap

Valence bond theory

a model of chemical bonding in which an electron-pair bond is formed between two atoms by the overlap of orbitals on the two atoms

valence bond theory

According to the valence bond theory, _ form when partially filled orbitals of two atoms overlap

Covalent bonds

Orbitals overlapping along the bond axis that connects two nuclei, forming an end-to-end type of overlap forms a _ bond

Sigma bond

A region of high electron concentration forms on the _

Bond axis

Simplest diatomic molecule

Hydrogen molecule (H2)

T or F valence P orbitals also form sigma bonds

True

_ and _ bonds form when more than one set of orbitals from the P sub-level overlap

Double and triple bonds

A side-to-side orbital overlap bond

Pi bond

For _ bonds, one of the bonds is a sigma bond formed by two lobes of two P orbitals overlapping end to end

Triple bonds

Strongest type of covalent bond (because the region of highest electron probability lies on the bond axis)

Sigma bonds

T or F Pi bonds are weaker than sigma bonds because the electrons are spread out over a greater volume of space around the bond axis

True (but I would so smash a pie rn)

The electrons in _ bonds are LESS attracted to the nuclei than in sigma bonds because the region of highest concentration is not along the binding axis, and so the electron pull on the nuclei at an angle

Pi bond

T or F triple bonds are stronger than either double or single bonds

True

Some molecules that no single Lewis structure can completely describe the distribution of electrons exhibit _

Resonance

When a molecule does NOT exist in one of the configurations, nor does it oscillate between the possible configurations

Resonance

The dotted lines in Lewis structures represent_

Half bonds

_ bonds do NOT oscillate between the two original molecules, but form a new one

Resonance bonds

T or F, some molecules form without an octet for each bonded atom.

True

The three situations in which some molecules form without an octet for each bonded atom.

The presence of an Odd number of valence electrons, electron deficiency, hypervalent molecules

T or F: some molecules have an odd number of valence electrons to share, so one atom can end up with seven electrons

True

Substances with these unpaired electrons are called _ which are fairly reactive

Free radicals

T or F elements can be content with fewer than four pairs of valence electrons (Boron)

True

T or F, in some molecules, the central atom has more than 8 valence electrons

True

Situations in which the central atom has more than eight valence electrons only occur in period_ and higher

3

Elements that have the ability to use D sub level electrons for bonding since the central atoms has more than 8 valence electrons

Molecules with an expanded octet

T or F, the valence bond theory can't explain ALL observations of a molecules certain shape

True

Theory that suggests that the atomic orbitals of a molecules atoms are replaced by totally new molecular orbitals when a molecule forms

Molecular orbital theory

This states that each atom's orbitals are replaced by totally new orbitals when a molecule forms.

Molecular orbital theory

The attraction of the molecule to a magnetic field

Paramagnetism

T or F: With the explanation of paramagnetism, molecules orbital theory correctly predicts the observed magnetic properties of diatomic oxygen

True

In molecular orbital theory, there are both _ and _ orbitals

Bonding and anti bonding

When electron waves constructively interfere, they reinforce each other and _ orbitals form between the nuclei

Bonding

The orbital that is lower in energy

Bonding

When atomic orbitals combine, both _ and _ orbitals form

Bonding and antibonding

If the electron waves destructively interfere with each other, an orbital forms on the outside of the molecule, far from the two nuclei. Higher in energy.

Anti bonding

_ spend little time between two nuclei and destabilize the molecule

Antibonding orbitals

T or F: if equal numbers of electrons inhabit bonding orbitals and antibonding orbitals, then NO BOND WILL FORM

true

Finally we're done with 8.1

I am too sick for this

One of the basic principles of electricity is that _ attract and _ charges repel

Opposite, like

T or F: electrons always repel, whether they are bonded or unbonded

True

_ determines the shape of molecules held together by covalent bonds

Charge repulsion

_ determines the arrangement of covalent bonds and unbonded pairs of electrons around the central atom

The repulsion of valence shell electrons in a molecule

What does VSEPR stand for?

Valence Shell Electron Pair Repulsion

Theory that focuses on the locations of high electron densities surrounding the central atom in a molecule

Valence shell electron pair revulsion theory (VSEPR)

In this model, regions of high electron density repel each other until they are separated by the maximum distance possible

VSEPR model

regions of high electron density repel each other until they are separated by the maximum distance possible, thus repulsion will establish the _

Bond angle

The shape in which four regions of electrons with four atoms bonded to the central atom. The angles between the bonds are 109.5°

Tetrahedral

Expected bond angle is 109.5°, shaped like a triangular pyramid, has four regions of electrons with three bonded atoms around the central atom

Regional pyramidal

One double bond and two single bonds. 3 regions of electrons produce bond angle of approximately 120°. 3 atoms surrounding the central atom. Y shaped molecule. All atoms in a singular plane.

Tritons planar

Two double bonds. 2 regions of electrons around the central atom. 180°. Ends point in opposite directions. Diatomic molecules

Linear molecule

Atom surrounded by four regions of electrons. 2 unbonded pairs and two single bonds. Either 109.5° or 120°

Bent molecule

The process by which new kinds of orbitals with equal energies form from a combination of orbitals with different energies

Orbital hybridization

T OR F- orbital hybridization is common between nonmetals, and even in medals involved in covalent bonding

True

T or F: promoting electrons to higher energy levels, requires extra energy

True

The main lobes of the individual hybrid orbitals are much larger than the lobes of _ or _ orbitals. They can point to and overlap the orbitals of other atoms more effectively, forming stronger bonds

S; p

T or F: other hybrids of S & P orbitals are possible

True

Since to P orbitals are involved, they are called
_

sp^2 hybrid orbitals

T or F: a more stable electron configuration is attained through hybridization, rather than by following the octet rule

True

Molecules that contain hybrid _ orbitals can form tetrahedral, regional pyramidal, and vent molecules because the number of hybrid orbitals formed is always equal to the number of s and p orbitals containing unpaired electrons after promotion

sp^3

T or F: we determine the shape of a molecule by looking at the arrangement of Adams around the central atom, not by looking at the unbonded pairs

True

If an sp3 hybrid (4 regions) has 2,3 or 4 numbers of bonds, the expected angle will be _

109.5°

If an sp3 hybrid (4 regions) has 1 number of bonds, the expected angle will be _

180°

If an sp2 hybrid (3 regions) has 2 or 3 numbers of bonds, the expected angle will be _

120°

If an sp hybrid (2 regions) has 1 or 2 numbers of bonds, the expected angle will be _

180°

Dipole moment: a measure of

Polarity

T or F: all bonds formed between atoms of different elements are polar to some extent

True

The magnitude of the bond polarity depends on the _ between the two elements

Electronegativity difference

The greater the difference in electronegativity, the more _ the bond will be

Polar

A molecule formed from a single polar bond will itself be polar- a _ - with distinct positive and negative partial charges

Polar molecule

If a molecule contains polar bonds, does that always mean that the molecule must be polar too?

Not always

T or F: the polarity of individual bonds may be quite high, but if those bonds are arranged, symmetrically the balance each other. As a result, the molecule overall is non-polar

True

The most significant features are the locations of the _ and _ partial charges

Positive and negative

For _ one end is predominantly negative and the other positive

Asymmetrical molecules

T or F: because of the distribution of attach Atoms on one side of the molecule, bent and trigonal pyramidal molecules have an asymmetrical electron density, resulting in molecules that are always polar
This rule is true even if all the outer atoms have the same electronegativity values

True

T or F: symmetrical molecules are not polar if the outer atoms are the same, but even symmetrical molecules are polar if the other atoms are different

True

If 4 atoms are bonded to the central atom, it is _, polar if outer atoms are different (four regions of electrons)

Tetrahedral

If 3 atoms are bonded to the central atoms, it is a _, always polar (four regions of electrons)

Trigonal pyramidal

If 3 atoms are bonded to the central atom, it is a _, Polar if outer atoms are different (3 regions of electrons)

Trigonal planar

If two atoms are bonded to the central atom, it is a _, always polar (4 regions of electrons)

Bent

If two atoms are bent to the central atom, it is a _ , always polar (3 regions of electrons)

Bent

If two atoms are bonded to the central atom, it is a _, polar if outer atoms are different (two regions of electrons)

Linear

If one atom is bonded to the central atom, it is a _ , polar if outer atoms are different (4 regions of electrons)

Linear

If one atom is bonded to the central atom, it is a _ , polar if outer atoms are different (3 regions of electrons)

Linear

If one atom is bonded to the central atom, it is a _ , polar if outer atoms are different (2 regions of electrons)

Linear

Scientists describe the magnitude and direction of molecular polarity with a quantity known as the _. It is the vector sum of all bond polarities that exist within the molecule (vector like that hottie from despicable me)

Molecular dipole moment

The _ factors in both the magnitude and direction of the bond polarities for each bond in the molecule.

Molecular dipole moment

The unit for dipole moments

Debye

T or F: the larger the value of the molecular dipole moment, the more polar, the bond or molecule will be

True

As with bond polarity, what is used to points from the more positive region of a molecule to the more negative region?

A crossed arrow (arrowhead pointing to the more negative region)

T or F: for the valence bond model in the molecular orbital model, neither of them accounts for all features of molecular bonds. scientist use the one that best explains a particular situation

True

What basic principal force governs VSEPR theory? What property of molecules is significantly affected by that principle?

-electrostatic repulsion of like charges
-molecular shapes

Explain what determines the bond angle and the shape of molecules in the VSEPR theory

the electron bond pairs and lone pairs on the center atom will help us predict the shape of a molecule. The shape of a molecule is determined by the location of the nuclei and its electrons.

Define polar molecule. They dissolve well in what solvent?

1) a molecule with an uneven distribution of charges in different regions of the molecule Molecules which have an unequal or uneven distribution of electrons yet no net charge
2) they dissolve in water because they form hydrogen bonds with water