ch. 6 - chemical bonding; section 5

Question 1

molecular geometry

Answer 1

3D arrangement of atoms in molecule, helping to make up its properties

Question 2

molecular polarity

Answer 2

unequal pull of electrons/uneven distribution of molecular shape
influences forces that act between molecules in liquids and solids

Question 3

how to tell if a molecule is polar?

Answer 3

if it has lone pairs on central atom or isn’t symmetrical

Question 4

VSEPR theory

Answer 4

• repulsion between sets of valence-level electrons surrounding an atom causing them to be oriented as far apart as possible
• minimizes repulsions of electrons while maximizing distance between them
• elements must be certain distance apart so they don’t push one another away
• predicts arrangement of electron pairs around each central atom and usually the correct arrangement of atoms in a molecule
• ONLY consider electron-pair repulsions

Question 5

lone pairs

Answer 5

exert greater repulsions and are less confined in space, reducing other bond angles or causing them to ‘bend’

Question 6

what is the difference between electron-pair geometry and molecular structure?

Answer 6

• electron-pair geometry includes lone electrons and bonded electrons; all regions where electrons are located
• molecular structure is the location of ATOMS, therefore excluding lone pairs

Question 7

what are the 5 molecular shapes and formulas?

Answer 7

• AB2 = linear, angles of 180 degrees
• AB3 = trigonal-planar, angles of 120 degrees
• AB4 = tetrahedron, angles of 109.5 degrees
• AB5 = trigonal bipyramidal, axial angles of 90 degrees, equatorial angles of 120 degrees
• AB6 = octahedron, all angles of 90 degrees

Question 8

hybridization

Answer 8

a model involving the mixing of two or more atomic orbitals of similar energies on the same atom to produce new hybrid atomic orbitals of equal energies

s + p = sp (2 hybrid orbitals)
s+p+p = sp2 (3 hybrid orbitals)
s+p+p+p = sp3 (4 hybrid orbitals)

Question 9

hybrid orbitals

Answer 9

orbitals of equal energy produced by the combination of two or more orbitals on the same atom

i. e. s and p orbitals combine together to create sp3 hybrid orbital
- sp2 = trigonal planar
- sp3 = tetrahedral
- sp3d = trigonal bipyramidal
- sp3d2 = octahedral

Question 10

intermolecular forces

Answer 10

the forces of attraction between molecules

Question 11

dipoles

Answer 11

• molecules that contain both positively and negatively charged regions
• created by equal but opposite charges that are separated by a short distance
• direction of dipole is from positive pole to negative pole
• a polar molecule can induce a dipole in a nonpolar molecule by temporarily attracting its electrons; this accounts for fact that nonpolar molecules, like oxygen, can dissolve in water

Question 12

dipole-dipole forces

Answer 12

• interactions between polar molecules

- molecules attract eachother with opposite charges/regions

Question 13

hydrogen bonding

Answer 13

• intermolecular force in which a hydrogen atom, bonded to a highly electronegative atom, is attracted to another highly electronegative tom on nearby molecule
• hydrogen can ONLY bond with fluorine, oxygen, or nitrogen

Question 14

london dispersion forces

Answer 14

• intermolecular attractions resulting from constant motion of electrons and the creation of instantaneous dipoles
• the connection between everything interacting with each other
• mainly on nonpolar molecules

Question 15

ion-dipole forces

Answer 15

ions interacting with polar molecules

Question 16

list the intermolecular forces in decreasing order of strength

Answer 16

1. Ion-Dipole
2. Hydrogen Bonding
3. Dipole-Dipole
4. London Dispersion

Question 17

list the trend in intermolecular forces

Answer 17

• high boiling point, high intermolecular force
• high surface tension, high intermolecular force
• high viscosity, high intermolecular force
• high vapor pressure, low intermolecular force

Question 18

bond angle

Answer 18

the angle between any two bonds that includes a common atom, measured in degrees

Question 19

bond length

Answer 19

the distance between nuclei of two bonded atoms along the straight line joining the nuclei

Question 20

order of electron pair repulsions/amount of space taken up from greatest to least

Answer 20

lone pair-lone pair > lone pair-bonding pair > bonding pair-bonding pair

lone pair > triple bonds > double bonds > single bonds

Question 21

how are dipole-dipole, london dispersion, and hydrogen bonding similar?

Answer 21

• all involve the shifting of the electron cloud to create a non-permanent dipole
• permanent dipoles are due to electronegativity differences (i.e. H20)