Chapter 12: Polarity and Symmetry and Hybridization

If the molecule has a net dipole moment, then it is ____.

polar

The greater the difference, the more _____ the bond until it becomes ionic.

polar

This bent molecule is asymmetrical, so dipole moments are asymmetrical and don't cancel. polar or non polar?

polar

h2o polar or non polar?

polar

bond? electrons are not shared equally, thus creating areas of partial positive and negative charge (δ + and δ -) within the molecule. But overall charge of the molecule is zero.

polar covalent

If it has different terminal atoms, then it is

polar.

To show polar covalent bond: 2) Or use an arrow pointing to more EN atom The smaller/greater the difference, the more nonpolar the bond type.

smaller

what things determine polarity of a molecule

Polarity of a molecule is determined by shape and symmetry of the molecule, as well as the orientation of polar bonds in the molecule.

how is H bonding represented

Represented by dotted lines connecting H on one molecule to unshared e pair of EN atom on another

Symmetrical, nonpolar shapes: With no lone pairs: _______ With lone pairs: ______

Symmetrical, nonpolar shapes: With no lone pairs: linear, trigonal planar, tetrahedral, trigonal bipyramidal, octahedral With lone pairs: square planar

____ molecule = uneven distribution of charge.

charge

Weakest of all IMF, exhibited by nonpolar molecules, atoms and noble gases.

dispersion forces

Number of orbitals involved in hybridization also determines ____ of a molecule

geometry

strongest imf

hydrogen bonding

bond? electrons move from one atom to another (or a group) to create oppositely charged particles. This creates electrostatic attraction and holds the compound together, overall charge of the compound is zero.

ionic

Forces of attraction between, rather than within, molecules - much weaker/stronger than ionic & covalent bonds (~1%).

weaker

If a molecule is symmetrical, (& bond polarities cancel out) →

→ it will be a nonpolar molecule

how to determine dipole, moments

(bond polarity: difference in EN between central and outer atoms: the greater the difference, the more polar the bond)

If a central atom has 2 ligands

- 2 sp hybrid orbitals (when 1 s + 1p hybridize)

Hybridization

- Explains how orbits of an atom become rearranged to allow for bonding

how to create a dipole

1 side of molecule is negative ; one side is slightly positive. * Creating a dipole.

lone pairs::polarity

2. Lone Pairs - tend to make a molecule polar. Remember to only look at what is on the central atom - outer atoms' lone pairs will not affect the overall polarity or symmetry.

If a central atom has 3 ligands

3 sp2 hybrid orbitals (1 s + 2p hybridize)

multiple bonds::polarity

3. Multiple bonds - could make a molecule polar, especially on the end of a chain.

If a central atom has 4 ligands

4 sp3 hybrid orbitals s + 3 p hybridize)

H bond has _% strength of an average covalent bond

5

If a central atom has 5 ligands

5 sp3d hybrid orbitals (1 s + 3p + 1d hybridize)

If a central atom has 6 ligands

6 sp3d2 hybrid orbitals (1 s + 3p + 2d hybridize)

Hybrid orbitals:

Blending (hybridization) of 2 or more atomic orbitals of different energies on the same atom to produce new bonding orbitals of equal energies.

how is bond type determined

Bond type is determined by the difference in electronegativity values.

Bonds between atoms of different elements are completely ionic or covalent. True or False?

Bonds between atoms of different elements are rarely completely ionic or covalent, they are somewhere in between.

if trying to show the Direction of the polar bond in a molecule, what can u do

Can use an arrow which points toward the more electronegative atom. Or show with lower case delta sign

All this happens along a spectrum, with the greatest EN difference being _____ (3.3). _____ is assigned a 100% ionic character, all else falls between this & 0 % (pure nonpolar covalent).

CsF

How do we know what the nature of a bond is?

Depends on each atom's attraction for electrons!

Ex. in Carbon: one 2s orbital combines with three 2p orbitals to form ______. The energy of the bonding orbitals is higher than s but lower than p.

Ex. in Carbon: one 2s orbital combines with three 2p orbitals to form 4 hybrid sp3 orbitals. The energy of the bonding orbitals is higher than s but lower than p.

If asymmetrical, (& bond polarities do not cancel out) → _______ molecule (caused by _______)

If asymmetrical, (& bond polarities do not cancel out) →polar molecule (caused by asymmetrical shape due to lone pairs or different bonding atoms)

If the structure is symmetric, then it is non-polar (provided that ______)

If the structure is symmetric, then it is non-polar (provided all terminal atoms are the same)

Dipole Moment

Molecule that has 2 poles (a separation of charge into oppositely charged regions) is said to have a dipole moment

HOW DO sp3 HYBRID ORBITALS FORM TO CREATE AMMONIA?

NH3 - N has valence electrons of 2s22p3 - yields 4 sp3 - one contains a lone pair and 3 have an unshared e for bonding

__________ = no difference in charge on outside of molecule. Electrons are evenly distributed. Uniform charge on outside of molecule.

NON-POLAR MOLECULES = no difference in charge on outside of molecule.

Nature of bond is determined by ______ difference between atoms

Nature of bond is determined by electronegativity (EN) difference between atoms (look at chart to find values)

Polar/Nonpolar molecules are not attracted to a magnetic field; Polar/Nonpolar molecules do align with an electric field

Nonpolar molecules are not attracted to a magnetic field; polar molecules do align with an electric field

dipole dipole interactions occur between _____ become weaker/stronger as distance increase.

Occurs between polar molecules- molecules that have permanent dipoles are attracted to each other. Molecules with dipole moments attract each other - the partial positive region of 1 molecule is attracted to the partial negative region of another & vice versa Become weaker as distance between molecules increases. These forces are really only important when the molecules are close to each other.

symmetry::polarity

Symmetry - in general, symmetrical molecules tend to be nonpolar IF all the outer atoms are the same. This is because the bond polarities will cancel each other out (equal and opposite directions). If all outer atoms are NOT the same, then molecule will be polar due to EN differences between central and outer atom. If the molecule is asymmetrical, the molecule will most likely be polar.

The attractions between molecules is stronger/weaker than the intramolecular attractions (bonds) that hold compounds together.

The attractions between molecules are not nearly as strong as the intramolecular attractions (bonds) that hold compounds together.

hydrogen bonding

The dipole-dipole interactions experienced when H is bonded to a very electronegative atom (such as N, O, or F) are unusually strong.

how do intermolecular forces affect properties?

They are, however, strong enough to control physical properties such as boiling and melting points, vapor pressures, and viscosities.

molecular shape- if shape is symmetrical, molecule tends to be _____ as ______ bonds cancel out if all outer atoms same. If molecule shape is asymmetrical, then molecule tends to be _____.

molecular shape- if shape is symmetrical, molecule tends to be nonpolar as polar bonds cancel out if all outer atoms same. If molecule shape is asymmetrical, then molecule tends to be polar.

This trigonal planar molecule has a symmetrical shape, so dipole moments are symmetrical and cancel out. polar or non polar?

non polar

To show polar covalent bond: 1) Use lower case Greek letter _____ to represent a partial charge - the more/less electronegative atom is partially negative end; more/less electronegative atom is partially positive end

To show polar covalent bond: 1) Use lower case Greek letter delta to represent a partial charge - the more electronegative atom is partially negative end; less electronegative atom is partially positive end

# of hybrid orbitals that form =

Total # ligands off a CENTRAL atom (bonds & lone pairs) = # of hybrid orbitals that form.

How does C form 4 identical bonds when it has 2s22p2 valence configuration?

Uses empty 2pz orbital so that s + 3 p orbitals hybridize to make 4 sp3 orbitals of equal energy, each with one unshared e for bonding.

what type of bond for each of these EN differences: 0-0.4 >0.4-1.0 >1.0-2.0 >2.0

non polar covalent slightly polar covalent polar covalent ionic

If it is linear or square planar, then it is

non-polar

1. When there are no lone pairs on the center atom, then the molecule is non-polar 2. If it is linear or square planar, then it is non-polar. Which rules overrides the other?

When there are no lone pairs on the center atom, then the molecule is non-polar 2. If it is linear or square planar, then it is non-polar. (This rule is more important than rule 1, so it overrules it because it has lone pairs.)

1. When there are no lone pairs on the center atom, then the molecule is non-polar 2. If it is linear or square planar, then it is non-polar. 3. If it has different terminal atoms, then it is polar. Which rule overrides the other two?

When there are no lone pairs on the center atom, then the molecule is non-polar 2. If it is linear or square planar, then it is non-polar. (This rule is more important than rule 1, so it overrules it because it has lone pairs.) 3. If it has different terminal atoms, then it is polar. (This rule overrules rule 1 and 2 because it is more important.)

When there are no lone pairs on the center atom, then the molecule is ____

non-polar

bf3, polar or non polar?

nonpolar

bond? electrons are all shared equally or nearly equally

nonpolar covalent

dispersion forces

While the electrons in the 1s orbital of helium would repel each other (and, therefore, tend to stay far away from each other), it does happen that they occasionally wind up on the same side of the atom. Electrons are in constant motion, and a temporary shifting of the electron cloud can occur within a nonpolar molecule. When moving electrons are on side of molecule close to neighbor, the charge causes neighbor's electrons to be momentarily on opposite side, creating an instantaneous dipole due to uneven electron distribution.

Asymmetrical, polar shapes

With lone pairs: bent (with 1 or 2 lone prs), trigonal pyramidal, see saw, T-shape, square pyramidal

which molecules exhibit IMF.

all

Repeating characteristics in polar molecules

asymmetrical shape (lone pairs) or Symmetrical shape, BUT asymmetrical atoms (terminal atoms are not all the same) so bond polarities do not cancel out

London dispersion forces, or dispersion forces, are

attractions between an instantaneous dipole and an induced dipole.