Ch. 1 - Structure and Bonding

Question 1

What is deuterium?

Answer 1

isotope of hydrogen (one proton, one neutron) (mass # = 2)

also relates to NMR spectroscopy!

Question 2

Where are most elements in organic chemistry found within the periodic table?

Answer 2

1st and 2nd rows (s and p orbitals)

Question 3

Which is higher in energy, s or p orbitals? Why?

Answer 3

p orbitals are higher in energy because the electron density is farther away (takes work to pull electron away, takes work to shield?)

Question 4

What is electronegativity?

Answer 4

tendency to gain electrons

Question 5

What is the formula for formal charge?

Answer 5

FC = val e- – (1/2 bonding + nonbonding e-)

Question 6

What is an isomer?

Answer 6

same molecular formula, different structure + molecule

Question 7

What atoms are common exceptions to octet rule? (BBPS)

Answer 7

boron and beryllium (2nd row; not enough e- in neutral molecule)
phosphorus, silver (3rd row; empty d orbitals, can have more than 8)

Question 8

Where is hydrogen placed for all oxyacids? (ex. HNO3)

Answer 8

it is placed on oxygen

Question 9

Where does organic chem assume hydrogens go?

Answer 9

on carbon

Question 10

What does “resonance stabilized” mean?

Answer 10

molecule has 2 or more resonance structures; negative charge is spread over molecule aka electrons are delocalized

Question 11

What is the formal charge of a single bonded oxygen with 3 lone pairs?

Answer 11

-1

Question 12

What is the formal charge of a double bonded oxygen with two lone pairs?

Answer 12

0

Question 13

What is curved arrow notation?

Answer 13

shows how electron position differs between structures

Question 14

What is a heteroatom?

Answer 14

an atom other than carbon or hydrogen

Question 15

What are the only things that vary for resonance strucutres?

Answer 15

lone pairs and pi bonds (and formal charge)

Question 16

What is the most electronegative element?

Answer 16

fluorine

Question 17

What is the 2nd most electronegative element?

Answer 17

oxygen

Question 18

What are the 3rd most electronegative elements?

Answer 18

nitrogen and chlorine

Question 19

What is a resonance hybrid?

Answer 19

composite of all possible resonance structures, electrons are delocalized

Question 20

Why can carbon form four bonds where it should only have two open p orbitals?

Answer 20

It hybridizes to 4 sp3 hybrid orbitals

Question 21

Which is stronger, a sigma bond or a pi bond?

Answer 21

a sigma bond is stronger because the electron density is closer to the nuclei (in between)

Question 22

What type of overlap occurs in sigma and pi bonds?

Answer 22

sigma = end-end 
pi = side-side

Question 23

What is conjugation?

Answer 23

• double/triple bonds that are separated by a single bond
• occurs whenever p orbitals can overlap 3 adjacent atoms
• conjugated systems have added stability

Question 24

What makes a better resonance structure?

Answer 24

• more bonds and fewer formal charges
• obeys octet rule
• negative charge is on more electronegative atoms
• positive charge is on less electronegative atoms
• PRIORITIZE OCTET

Question 25

What is the difference between a shell and an orbital?

Answer 25

``` Shell = principal quantum number/orbit Orbital = actual electron density ```

Question 26

How many orbitals are in the first shell?

Answer 26

one

Question 27

Where is most of the volume of an atom contained?

Answer 27

electron cloud

Question 28

Does a chemical bond produce a system of higher or lower energy?

Answer 28

lower

Question 29

Atoms bond in order to achieve a full shell of _____ electrons, leading to a system that has _____ energy and increased stability, compared to the unbonded atoms.

Answer 29

valence; decreased

Question 30

T or F: A p orbital has the greatest electron density at the nucleus.

Answer 30

F, A p orbital has a node (region of zero electron density) at the nucleus.

Question 31

What is a constitutional isomer?

Answer 31

An isomer that has different connectivities (same molecular formula)

Question 32

T or F: Halogens are usually placed in the periphery of the molecule because they only form one bond.

Answer 32

False. That's hydrogen.

Question 33

T of F: B and Be do not have sufficient electrons to have an octet.

Answer 33

True

Question 34

T or F: A resonance hybrid is a single structure.

Answer 34

True. It does not fluctuate between the resonance forms.

Question 35

What two things determine an atom's geometry?

Answer 35

bond angle and bond length

Question 36

What is the basic principle of VSEPR theory?

Answer 36

groups around an atom are located as far from each other as possible

Question 37

T or F: The number of unpaired (single) electrons in a resonance structure cannot change.

Answer 37

True

Question 38

T or F: Lone pairs are omitted in condensed structures.

Answer 38

True (double check!)

Question 39

What two things does a charge on an atom indicate in a skeletal structure?

Answer 39

the number of covalent bonds and nonbonded electrons pairs at that atom

Question 40

What type of symmetry does a sigma bond have?

Answer 40

cylindrical symmetrical

Question 41

What is the ground state of an atom?

Answer 41

the lowest energy state of an atom where all electrons are in their lowest energy level

Question 42

When drawing a condensed structure of an organic compound, multiple bond lines are usually ______ while single bond lines are often ______.

Answer 42

Included, omitted

Question 43

For a carbon-carbon triple bond, what oritals overlap to form a sigma bond?

Answer 43

sp

Question 44

Unhybridized p orbitals are at what angle towards hybrid orbitals?

Answer 44

right angle

Question 45

T or F: Electronegativity is a relative quantity?

Answer 45

true

Question 46

What is the electronegative scale values?

Answer 46

0 to 4

Question 47

What is percent s character in sp, sp2 and sp3?

Answer 47

50%, 33%, 25%

Question 48

T or F: Any carbon-hydrogen bond is always considered to be polar.

Answer 48

False

Question 49

T or F: Pi bonds in a triple bond are perpendicular planes to each other.

Answer 49

true

Question 50

REMEMBER: Whenever C or H are bonded to O or N and halogens, they are polar!

Answer 50

Remember this!