Chapter 1

Question 1

define constitutional isomer

Answer 1

constitutional isomers are compounds with the same molecular formula but a different arrangement of internal atoms. they have different physical properties and different names.

Question 2

How many bonds does H or F,Cl,Br,I tend to form? What is that called?

Answer 2

monovalent - generally forms 1 bond

Question 3

How many bonds does O tend to form? What is that called?

Answer 3

divalent - generally forms 2 bonds

Question 4

How many bonds does N tend to form? What is that called?

Answer 4

trivalent - generally forms 3 bonds

Question 5

How many bonds does C tend to form? What is that called?

Answer 5

tetravalent - generally forms 4 bonds

Question 6

define covalent bond

Answer 6

two atoms sharing a pair of electrons

Question 7

define lone pair

Answer 7

a pair of electrons that is not share between two atoms in a molecule. that is, they are only associated with 1 atom.

Question 8

define octet rule

Answer 8

the octet rule says that second row elements will try to form the necessary number of bonds to fill all 8 “spots” for an electron around each of those atoms (can also go down to 8 in next-to-last shell)

Question 9

define formal charge. explain how to calculate it.

Answer 9

formal charge is associated with an atom that does not exhibit the appropriate # of valence electrons. a bond contributes 1 electron to an atom. a lone pair contributes 2 electrons to an atom. if the atom does not “have” enough electrons to balance out the nucleus, then it will have a formal charge

Question 10

define electronegativity

Answer 10

electronegativity is a measure of the ability of an atom to attract electrons

Question 11

in what directions does electronegativity increase?

Answer 11

Question 12

what is the electronegativity of Hydrogen?

Answer 12

2.1

Question 13

what is the electronegativity of Carbon?

Answer 13

2.5

Question 14

what is the electronegativity of Nitrogen?

Answer 14

3.0

Question 15

what is the electronegativity of Oxygen?

Answer 15

3.5

Question 16

what is the electronegativity of Chlorine?

Answer 16

3.0

Question 17

what are the (roughly) 3 types of intramolecular bonds?

Answer 17

covalent bond

polar covalent bond

ionic bond

Question 18

describe a covlent bond. what approximate difference in electronegativities results in a covalent bond?

Answer 18

in a covalent bond, electrons are considered to be shared “equally” between the 2 atoms. the difference in electronegativity is 0.5.

Question 19

describe a polar covlent bond. what approximate difference in electronegativities results in a polar covalent bond?

Answer 19

electrons are not shared equally between the atoms. the difference is electronegativity is between 0.5 and 1.7

Question 20

describe an ionic bond. what approximate difference in electronegativities results in an ionic bond?

Answer 20

electrons are not shared at all between the atoms. (salt) the difference in electronegativity is greater than 1.7

Question 21

describe induction

Answer 21

induction is the movement of electrons towards a more electronegative atom, resulting in a partial charge.

Question 22

define electron density

Answer 22

electron density is the probability of finding an electron in a particular region of space

Question 23

describe an orbital (quantum mechanically)

Answer 23

Question 24

define atomic orbital and list 4 types of atomic orbital

Answer 24

an atomic orbital is an orbital with respect to the nucleus of a single atom. examples include the s, p, d, and f orbitals.

Question 25

what do simple s and p orbitals look like?

Answer 25

Question 26

what is a node?

Answer 26

Question 27

what are degenerate orbitals?

Answer 27

degenerate orbitals are orbitals with the same energy level (for example: 2p_x , 2py , and 2p_z )

Question 28

what three pinciples/rules govern the way that orbitals are filled?

Answer 28

1. Afbau Principle - the lowest energy orbital is filled first 2. Pauli exclusion principle - each orbital can accommodate a maximum of 2 electrons that have opposite spin 3. Hund's Rule - for degenerate orbitals (like p), one electron is placed in each degenerate orbital first, before the elctrons are paired up

Question 29

what is the difference between valence bond theory and molecular orbital theory?

Answer 29

valence bond theory is a simple way of describing how atomic orbitals overlap, while molecular orbital theory is a complex way of describing how atomic orbitals overlap.

Question 30

how are nodes generated (in valence bond theory)?

Answer 30

valence bond theory treats the atomic orbitals as waves. when these waves have equal and opposite magnitude, that creates a node.

Question 31

what is a sigma bond?

Answer 31

a sigma bond is an intramolecular bond characterized by circular symmetry with respect to the bond axis. all _single_ bonds are sigma bonds.

Question 32

describe molecular orbital theory

Answer 32

molecular orbital theory uses math to describe the _new molecular orbitals_ formed from overlapping atomic orbitals (more complex)

Question 33

how many molecular orbitals do you get when combining 2 atomic orbitals? 3 atomic orbitals?

Answer 33

2 and 3, respectively. of orbitals in = # of orbitals out

Question 34

describe difference molecular orbitals.

Answer 34

the **antibonding MO** has the higher energy. it is formed from destructive interference. it has 2 vertical nodes. the **nonbonding** **MO** has the middle energy. it has 1 vertical node. (the one that doesn't form for 2 in --\> 2 out) the **bonding MO** has the lower energy. it is formed from constructive interference. it has no vertical nodes.

Question 35

what does HOMO stand for?

Answer 35

highest occupied molecular orbital

Question 36

what does LUMO stand for?

Answer 36

lowest unoccupied molecular orbital

Question 37

how are the sp, sp², and sp³ hybrid orbitals formed? what is different about this than filling atomic orbitals?

Answer 37

the difference is that all of the orbitals are filled with only one electron (before one with opposite spin is added), even the s orbital

Question 38

what geometry (both electron and atom) do the hybridized orbitals result in?

Answer 38

Question 39

what is a pi bond?

Answer 39

a pi bond is formed from the overlap of p-orbitals (spare orbitals after hybridization). a double bond has 1 pi bond; a triple bond has 2 pi bonds.

Question 40

what is the relationship between # of bonds, bond strength, and bond length?

Answer 40

as # of bonds increases (double and triple bonds), bond length decreases, and bond strength increases

Question 41

define steric number

Answer 41

steric number is the total number of (sigma) bonds and lone pairs around one atom

Question 42

(VSEPR theory) which repels more strongly, lone pairs or bonds?

Answer 42

lone pairs repel more strongly

Question 43

what angle corresponds to a tetrahedral arrangement of atoms? (VSEPR theory)

Answer 43

approx. 109.5 degrees

Question 44

what angle corresponds to a trigonal pyramidal arrangement of atoms? (VSEPR theory)

Answer 44

approximately 109.5 degrees (or slightly less)

Question 45

what angle corresponds to a trigonal planar arrangement of atoms? (VSEPR theory)

Answer 45

approximately 120 degrees

Question 46

what angle corresponds to a linear arrangement of atoms? (VSEPR theory)

Answer 46

approximately 180 degrees

Question 47

what angle corresponds to an sp³ bent arrangement of atoms? (VSEPR theory)

Answer 47

approximately 109.5 degrees

Question 48

describe dipole moment and give formula

Answer 48

the dipole moment is an _indicator of polarity_, based on the amount of partial charge on either end of the dipole & the distance of separation. both _bonds_ and _lone pairs_ can have associated dipole moments.

Question 49

what are typical magnitudes of: dipole moment partial charge distance for the dipole moment calculation?

Answer 49

dipole moment -- 10^-18 esu cm partial charge -- 10^-10 esu distance -- 10^-8 cm

Question 50

what is a debye?

Answer 50

1 debye (D) = 10^-18 esu cm

Question 51

define percent ionic character

Answer 51

% ionic character = observed dipole moment ------------------------------------------------------------------------ calculated dipole moment (as if it were 100% ionic)

Question 52

what is a molecular dipole moment?

Answer 52

a molecular dipole moment (net dipole moment) is the vector sum of all dipole moments in a molecule

Question 53

define intermolecular forces

Answer 53

intermolecular forces are the attractive forces between molecules. they determine the physical properties of the compound.

Question 54

describe dipole-dipole interactions

Answer 54

compounds with net dipole moments can either repel or attract in solid phase, molecules line up to attract each other. in liquid phase, moleculaes are free to tumble but tend to move so that they attract more often than they repel.

Question 55

what is the relationship between net dipole moment and melting/boiling point?

Answer 55

as the net dipole moment increases, the melting & boiling points increase

Question 56

describe hydrogen bonding

Answer 56

hydrogen bonding is not a bond, but a specific (strong) _type of dipole-dipole interaction_ occurs when a _hydrogen atom_ is connected to a (strongly) _electronegative atom_ the hydrogen atom will bear a partial positive charge because of induction. this partial + can then interact with a lone pair (partial -) in a neighboring molecule. strong bond b/c hydrogen is a _very small atom_ & thus can get very close to the other molecule

Question 57

what is a protic compound?

Answer 57

a protic compound is any compound with a proton (H) connected to an electronegative atom

Question 58

describe London Dispersion Forces (van der Waals Forces)

Answer 58

London/van der Waals forces are a fleeting, weak attraction between 2 molecules due to a fleeting dipole-dipole moment in one molecule inducing a fleeting dipole-dipole moment in a nearby molecule

Question 59

how do fleeting dipole moments form in molecules?

Answer 59

large hydrocarbons (or other molecules with no strongly electronegative atoms) have an _average dipole moment of zero_. however, as the _electrons move around_ the molecule, it can _momentarily_ have a _dipole moment_.

Question 60

which experiences stronger London dispersion forces-- a larger hydrocarbon or a smaller hydrocarbon?

Answer 60

larger hydrocarbons --\> more surface area --\> experiences stronger London dispersion forces

Question 61

which experiences stronger London dispersion forces-- a heavier hydrocarbon or a lighter hydrocarbon?

Answer 61

heavier hydrocarbons --\> more surface area --\> experiences stronger London dispersion forces

Question 62

which experiences stronger London dispersion forces-- a branched hydrocarbon or a "straight" hydrocarbon?

Answer 62

"straight" a _branched hydrocarbon experiences fewer_ London dispersion forces: branched hydrocarbons --\> decreased surface area --\> fewer London dispersion forces

Question 63

describe solubility

Answer 63

for compounds, solubility is a measure of how well they dissolve in a solvent. _like dissolves like:_ polar compounds are more soluble in polar solvents nonpolar compounds are more soluble in nonpolar solvents

Question 64

what makes soap special?

Answer 64

soap has both polar and nonpolar ends. the nonpolar ends surround the oil, forming a sphere of soap molecules with the polar tails facing the water