Chem chapter 8 exam 4

Question 1

octet rule exceptions

Answer 1

odd-electron species
incomplete octet
expanded valance shell

Question 2

odd electron species (octet rule exception)

Answer 2

-an octet can’t be achieved if there are an odd-number of electrons in a compound
-they have free radicals, or an unpaired electron, which makes the atom/compound more reactive

Question 3

incomplete octet (octet rule exceptions)

Answer 3

boron is generally stable with 6 electrons

Question 4

expanded valance shell (octet rule exceptions)

Answer 4

-elements (the central atom) in row 3 or lower can expand their valance shell to hold more than eight electrons
-can help reduce formal charges`

Question 5

in organic lewis structures, the carbons…

Answer 5

connect to each other and the non-carbons connect to the carbons

Question 6

electron geometry

Answer 6

the geometry of all of the atoms and the electrons in a compound

Question 7

molecular geometry

Answer 7

the geometry of the atoms in a compound (still affected by the lone pairs)

Question 8

how to determine electron groups

Answer 8

how many bonding pairs and lone pairs there are
for example, in NH3, the lewis structure has 3 lines and 1 set of lone pairs on the central atom, so they have 4 electron groups

Question 9

2 electron groups

Answer 9

linear

Question 10

3 electron groups

Answer 10

trigonal planar

Question 11

4 electron groups

Answer 11

tetrahedral

Question 12

5 electron groups

Answer 12

trigonal bipyramidal

Question 13

6 electron groups

Answer 13

octahedral

Question 14

molecular geometry: linear with zero lone pairs

Answer 14

] linear
] 180 degrees

Question 15

molecular geometry: trigonal planar with zero lone pairs

Answer 15

] trigonal planar
] 120 degrees

Question 16

molecular geometry: trigonal planar with one lone pairs

Answer 16

] bent
] <120 degrees

Question 17

molecular geometry: tetrahedral with zero lone pairs

Answer 17

] tetrahedral
] 109.5 degrees

Question 18

molecular geometry: tetrahedral with one lone pairs

Answer 18

] trigonal pyramidal
] <109.5 degrees

Question 19

molecular geometry: tetrahedral with two lone pairs

Answer 19

] bent
] <109.5 degrees

Question 20

molecular geometry: trigonal bipyramidal with zero lone pairs

Answer 20

] trigonal bipyramidal
] 120 degrees, 90 degrees

Question 21

molecular geometry: trigonal bipyramidal with one lone pairs

Answer 21

] seesaw
] <120 degrees, 90 degrees

Question 22

molecular geometry: trigonal bipyramidal with two lone pairs

Answer 22

] T-shaped
] 180 degrees, 90 degrees

Question 23

molecular geometry: trigonal bipyramidal with three lone pairs

Answer 23

] linear
] 180 degrees

Question 24

molecular geometry: octahedral with zero lone pairs

Answer 24

] octahedral
] 90 degrees

Question 25

molecular geometry: octahedral with one lone pairs

Answer 25

] square pyramidal ] 90 degrees

Question 26

molecular geometry: octahedral with two lone pairs

Answer 26

] square planar ] 90 degrees

Question 27

when looking at a molecule with multiple central atoms, how can we find the electron geometry?

Answer 27

look at each central atom and count for lone and boding pairs

Question 28

no or very little difference in electronegativity (EN)

Answer 28

covalent

Question 29

moderate difference in EN

Answer 29

polar covalent

Question 30

large difference in EN

Answer 30

ionic

Question 31

ΔEN less than or equal to 0.4

Answer 31

covalent

Question 32

ΔEN between 0.4 and 1.8

Answer 32

polar covalent

Question 33

ΔEN greater than 1.8

Answer 33

ionic

Question 34

in a polar covalent bond, the bonds...

Answer 34

involve unequal sharing of electrons, which will result in partial charges - the more EN will have more of a (-) charge and the less EN will have more of a (+) charge

Question 35

polar covalent bonds on pictures of the molecule

Answer 35

more blue means more (+) so less e- more red means more (-) with means more e-

Question 36

a polar bond dosent always mean the molecule is polar because it requires a ... and a polar bond creates a ...

Answer 36

-it requires a net dipole moment -a polar bond creates a dipole, but the molecular geometry can cancel it out

Question 37

for a polar molecule, there must be...

Answer 37

- must have a polar bond - the polar bonds must not cancel out (usually happens when the electron and molecular geometry match) for example: o=c=o, the oxygens are more EN and pull on opposite sides of the carbon, but since there is a pull on both sides, they cancel out and the bond is non polar.

Question 38

bond order

Answer 38

the number of bonding electron pairs shared by two atoms in a molecule - single bonds: 1 - double bonds: 2 -triple bonds: 3

Question 39

higher order bonds vs lower order bonds

Answer 39

higher order bonds: shorter and stronger lower order bonds: weaker and longer bonds

Question 40

why do we get short order bonds

Answer 40

more electrons shared between two elements results in more overlap between the electron clouds thus shorter

Question 41

why do we have stronger order bonds

Answer 41

more electrons shared in bonds between two elements requires more energy to break thus stronger

Question 42

a single bond is

Answer 42

the longest and weakest

Question 43

a double bond is

Answer 43

in the middle with length and strength

Question 44

a triple bond is

Answer 44

the shortest and strongest

Question 45

bond length and atomic radii

Answer 45

when comparing between different pairs of elements depend on the atomic radii - smaller elements make shorter bonds

Question 46

bond order formula=

Answer 46

(number of shared pairs in all X-Y bonds)/ (number of X-Y links in the molecule or ion) or think of it as number of lines divided by the groups of lines

Question 47

average bond energy (KJ/mol)

Answer 47

the amount of energy to break a bond and these are endothermic since you need energy going into the compound to break the bond(s)

Question 48

heats or reaction to get average bond energies

Answer 48

Σ(BE reactants)- Σ(BE products)

Question 49

how can you tell if a reaction is endo or exothermic

Answer 49

-if the reactants have weak bonds and the products have strong bonds, exothermic -if the reactants have strong bonds and the products have weak bonds, endothermic