Structure and Bonding

Question 1

How is the quantum theory of atomic
structure differs from the Bohr’s theory?

Answer 1

The quantum theory explains that electrons
are in 3-dimensional shaped electron clouds that
represent the probability of an electron’s
location. Bohr’s theory explains that the
electrons are in orbits or shells.

Question 2

What is the difference between an
orbit and an orbital?

Answer 2

Orbit is the idea of an electron “orbiting” the
nucleus like planets orbiting the sun. Orbitals are electron clouds that represent the shape of probability for an electron’s location.

Question 3

What do electron configurations tell us
about the atom?

Answer 3

It tells about the detailed location of
electrons in an atom, the specific electron
orbitals that the electrons are found.

Question 4

How many orbitals are in the fourth
energy level?

Answer 4

The 4th level contains s, p, d, and f orbitals,
so the total number of orbitals is 16.

Question 5

How many orbitals of each type are
there? For s, p, d, and f?

Answer 5

s – 1
p – 3
d – 5
f - 7

Question 6

______ of more than 30 million chemical compounds contain carbon.

Answer 6

90%

Question 7

Origins of Organic Chemistry, Why is it so special?

Answer 7

Carbon is group 4A element, it can share 4 valence electrons and form 4
covalent bonds.

Question 8

Who is often credited as
the father of modern
atomic theory?

Answer 8

John Dalton

Question 9

Postulates by john Dalton

Answer 9

1. Indivisibility of atom (WRONG)
2. All atoms of the same element are
   identical (WRONG; isotopes)
3. Different elements have very different
   types of atoms or differ in all respects
   (WRONG; isobars)

Question 10

Who proposed the
planetary model of the
atom?

Answer 10

Niels Bohr

Question 11

Planetary Model of the Atom, Main point

Answer 11

1. Electrons orbit the nucleus in
   orbits that have a set size and
   energy. (WRONG)
2. The energy of the orbit is
   related to its size.
3. Radiation is absorbed or
   emitted when an electron moves
   from one orbit to another.

Question 12

It states that there is an inherent
uncertainty in the act of measuring a
variable of a particle.

Answer 12

Heisenberg Uncertainty Principle

Question 13

Originally, electrons were thought to orbit around the nucleus in defined paths

Answer 13

Electron orbit model

Question 14

It was discovered that electrons move in waves in a defined space called an electron cloud

Answer 14

Electron cloud model

Question 15

Structure of an atom: small diameter

Answer 15

(2 X 10-10 m = 200 pm)

Question 16

very dense; contains protons and neutrons

Answer 16

Nucleus

Question 17

Diameter of nucleus

Answer 17

small (10-15 m)

Question 18

located in space remindful of a cloud (10-10 m) around nucleus

Answer 18

Electrons

Question 19

number of protons in nucleus

Answer 19

The atomic number (Z):

Question 20

number of protons plus neutrons

Answer 20

The mass number (A):

Question 21

All atoms of same element have the same

Answer 21

Z value

Question 22

atoms of the same element with different
numbers of neutrons and thus different A.

Answer 22

Isotopes:

Question 23

(atomic weight) of an
element is weighted average mass in atomic
mass units (amu) of an element’s naturally
occurring isotopes.

Answer 23

atomic mass

Question 24

There are four different kinds of orbitals for
electrons based on those derived for a hydrogen
atom
▪ Denoted

Answer 24

s, p, d, and f

Question 25

spherical, nucleus at center

Answer 25

s orbitals:

Question 26

dumbbell-shaped, nucleus at middle

Answer 26

p orbitals:

Question 27

elongated dumbbell-shaped, nucleus at center

Answer 27

d orbitals:

Question 28

tetrahedral, nucleus at center

Answer 28

f orbitals:

Question 29

Orbitals are grouped in ______ of increasing size and energy

Answer 29

shells

Question 30

Each orbital can be occupied by ____________

Answer 30

two electrons.

Question 31

Third shell contains an s orbital (3s), three p orbitals (3p), and five d orbitals (3d), holds ______ electron

Answer 31

18

Question 32

Second shell contains one s orbital (2s) and three p orbitals (2p), holds _____ electrons

Answer 32

eight

Question 33

Lobes of a p orbital are separated by region of zero electron density,

Answer 33

node.

Question 34

(i.e., lowest energy arrangement) of an atom ▪ lists orbitals occupied by its electrons.

Answer 34

Ground-state electron configuration

Question 35

Rules ground-state electron configuration

Answer 35

1. Lowest-energy orbitals fill first: 2. Electrons act as if they were spinning around an axis. Electron spin can have only two orientations, up  and down . Only two electrons can occupy an orbital, and they must be of opposite spin 3. If two or more empty orbitals of equal energy are available, electrons occupy each with spins parallel until all orbitals have one electron

Question 36

Principle in 1. Lowest-energy orbitals fill first:

Answer 36

(Aufbau (“build-up”) principle)

Question 37

Principle in Electrons act as if they were spinning around an axis. Electron spin can have only two orientations, up  and down . Only two electrons can occupy an orbital, and they must be of opposite spin

Answer 37

(Pauli exclusion principle)

Question 38

Principle: 3. If two or more empty orbitals of equal energy are available, electrons occupy each with spins parallel until all orbitals have one electron

Answer 38

(Hund's rule).

Question 39

Atoms form bonds because

Answer 39

the resulting compound is more stable than the separate atoms

Question 40

Ionic bonds in salts form by

Answer 40

electron transfers

Question 41

(electron dot) show valence electrons of an atom as dots

Answer 41

Lewis structures

Question 42

have a line drawn between two atoms indicating a 2 e- covalent bond.

Answer 42

Kekulé structures

Question 43

Stable molecule results at completed shell,

Answer 43

octet (eight dots) for main-group atoms (two for hydrogen)

Question 44

Atoms with one, two, or three valence electrons form

Answer 44

one, two, or three bonds, respectively.

Question 45

Atoms with four or more valence electrons form as many bonds as electrons needed to fill the s and p levels of their valence shells to reach a _____________

Answer 45

stable octet.

Question 46

Carbon has four valence electrons (2s 2 2p 2 ), forming ________

Answer 46

four bonds

Question 47

Valence electrons not used in bonding are called

Answer 47

nonbonding electrons, or lone-pair electrons

Question 48

forms when two atoms approach each other closely so that a singly occupied orbital on one atom overlaps a singly occupied orbital on the other atom

Answer 48

Covalent bond

Question 49

Two models to describe covalent bonding:

Answer 49

▪ Valence bond theory ▪ Molecular orbital theory

Question 50

Electrons are paired in the overlapping orbitals and are attracted to nuclei of both atoms ▪ H–H bond results from the overlap of two singly occupied hydrogen 1s orbitals

Answer 50

Valence Bond Theory:

Question 51

H-H bond is cylindrically symmetrical,

Answer 51

sigma (s) bond

Question 52

H–H has bond strength of

Answer 52

436 kJ/mol

Question 53

is a factor that leads to maximum or minimum stability.

Answer 53

Distance between nuclei

Question 54

If too close, they repel because both are

Answer 54

positively charged

Question 55

If too far apart, bonding is

Answer 55

weak

Question 56

independently observed that carbon always has four bonds

Answer 56

Kekulé and Couper

Question 57

proposed that the four bonds of carbon have specific spatial directions

Answer 57

van't Hoff and Le Bel

Question 58

sp3 hybrid orbitals: an s orbital and three p orbitals combine to form four

Answer 58

equivalent, unsymmetrical, tetrahedral orbitals

Question 59

C–H bond has a strength of ______ and a length of _____ pm

Answer 59

439 kJ/mol and 109 pm

Question 60

The remaining p orbital in sp2 is

Answer 60

perpendicular to the plane

Question 61

Two sp2 -hybridized orbitals overlap to form a

Answer 61

s bond.

Question 62

Two sp2 -hybridized orbitals overlap to form a

Answer 62

sigma bond

Question 63

Electrons in the s bond are

Answer 63

centered between nuclei

Question 64

Electrons in the sigma bond

Answer 64

occupy regions are on either side of a line between nuclei

Question 65

Ethylene C=C bond length ____

Answer 65

134 pm

Question 66

sp orbital placement of tow p-orbitals

Answer 66

perpendicular to the y and z axis

Question 67

H–N–H bond angle in ammonia (NH3)

Answer 67

107.3°

Question 68

C-N-H bond angle is

Answer 68

110.3 °

Question 69

where electrons are most likely to be found (specific energy and general shape) in a molecule

Answer 69

molecular orbital

Question 70

MO is lower in energy

Answer 70

Additive combination

Question 71

MO is higher in energy

Answer 71

Subtractive combination

Question 72

is from combining p orbital lobes with the same algebraic sign

Answer 72

The additive bonding MO

Question 73

is from combining lobes with opposite signs

Answer 73

The  antibonding MO

Question 74

don’t have C-H or C-C single bonds shown. They are understood.

Answer 74

Condensed structures

Question 75

Drawing Skeletal Structures (Commonly Used)

Answer 75

1) Carbon atoms aren’t usually shown 2) A carbon atom is assumed to be at each intersection of two lines (bonds) and at the end of each line. 3) Hydrogen atoms bonded to carbon aren’t shown. 4) Atoms other than carbon and hydrogen ARE shown

Question 76

Electrons occupy ______ around the nucleus.

Answer 76

orbitals