chem121test5

Question 1

Ionic chemical bonds

Answer 1

Electrostatic attraction between ions

Question 2

Covalent chemical bonds

Answer 2

Sharing of electrons

Question 3

Metallic chemical bonds

Answer 3

Free electron hold metal atoms together

Question 4

Lewis Symbols

Answer 4

a method to denote potential bonding electrons by using one dot for every valence electron around the element symbol

Question 5

the octet rule

Answer 5

atoms tend to gain, lose, or share electrons until they are surrounded by eight valence electrons

Question 6

Ionic Bonding

Answer 6

Metals and nonmetals (except group 8A)
One element readily gives up an electron (has a LOW ionization energy).
Another element readily gains an electron (has a HIGH electron affinity).
Arrow(s) indicate the transfer of the electron(s).

Question 7

Ionic Bonding is

Answer 7

Very exothermic

Question 8

Lattice Energy

Answer 8

Energy required to completely separate one mole of a solid ionic compound into its gaseous ions.
That amount of energy is RELEASED to MAKE the ionic compound (in the Born–Haber cycle)

Question 9

Born–Haber Cycle

Answer 9

Many factors affect the energy of ionic bonding.
Start with the metal and nonmetal elements: Na(s) and Cl2(g).
Make gaseous atoms: Na(g) and Cl(g).
Make ions: Na+(g) and Cl–(g).
Combine the ions: NaCl(s)

Question 10

This makes the formation of salts from the elements

Answer 10

exothermic

Question 11

It takes energy to convert the elements to

Answer 11

atoms

Question 12

Lattice energy increases with

Answer 12

Increasing charge on the ions
Decreasing size
of ions

Question 13

Properties of Ionic Substances

Answer 13

Evidence of well-defined 3-D structures:
Brittle
High melting points
Crystalline
Cleave along smooth lines

Question 14

Transition metals do NOT

Answer 14

follow the Octet rule

Question 15

Transition metals lose

Answer 15

Transition metals lose the VALENCE (s) electrons FIRST, THEN lose the d- electrons necessary for the given ion charge

Question 16

For a covalent bond to form

Answer 16

the attractions between the atoms must be greater than the repulsions

Question 17

Bonding pairs

Answer 17

shared electrons in a Lewis structure; they can be represented by two dots or one line, NOT both!

Question 17

Lone pairs (non-bonding pairs)

Answer 17

electrons located on only one atom in a Lewis structure

Question 18

single bonds

Answer 18

when atoms share only one pair of electrons

Question 19

double bonds

Answer 19

when atoms share two electron pairs

Question 20

triple bonds

Answer 20

when atoms share three pairs of electrons

Question 21

Bond polarity

Answer 21

a measure of how equally or unequally the electrons in a covalent bond are shared

Question 22

nonpolar covalent bond

Answer 22

the electrons are shared equally

Question 23

polar covalent bond

Answer 23

one of the atoms attracts electrons to itself with a greater force

Question 24

Electronegativity

Answer 24

the ability of an atom in a molecule to attract electrons to itself

Question 25

electronegativity generally increases

Answer 25

>^

Question 26

Less that 0.5

Answer 26

non-polar covalent

Question 27

2.0 and above

Answer 27

ionic

Question 28

(2.0-0.5) otherwise

Answer 28

polar covalent

Question 29

dipole

Answer 29

two equal, but opposite, charges are separated by a distance

Question 30

dipole moment

Answer 30

produced by two equal but opposite charges separated by a distance, r, is calculated,

Question 31

dipole moments are measured in

Answer 31

debyes (D)

Question 32

Is a Compound Ionic or Covalent?

Answer 32

Simplest approach: Metal + nonmetal is ionic; nonmetal + nonmetal is covalent. There are many exceptions: It doesn’t take into account oxidation number of a metal (higher oxidation numbers can give covalent bonding). Electronegativity difference can be used; the table still doesn’t take into account oxidation number. Properties of compounds are often best: Lower melting points mean covalent bonding, for example.

Question 33

Formal charge

Answer 33

the charge an atom would have if all of the electrons in a covalent bond were shared equally

Question 34

Formal charge equation

Answer 34

(valence electrons) – ½ (bonding electrons) – (all nonbonding electrons)

Question 35

Average Bond Enthalpies

Answer 35

These are averages over many compounds; not every bond for a pair of atoms has the same bond energy

Question 36

Multiple bonds are

Answer 36

stronger than single bonds

Question 37

As the number of bonds between two atoms increases,

Answer 37

the bond length decreases

Question 38

Resonance structures

Answer 38

uses multiple structure to describe a molecule

Question 39

Localized electrons

Answer 39

specifically on one atom or shared between two atoms

Question 40

delocalized electrons

Answer 40

electrons are shared by multiple atoms

Question 41

Exceptions to the Octet Rule

Answer 41

Ions or molecules with an odd number of electrons Ions or molecules with less than an octet Ions or molecules with more than eight valence electrons (an expanded octet)

Question 42

hypervalent

Answer 42

when atoms in periods 3 through 6 use d-orbitals to make more than four bonds

Question 43

Linear

Answer 43

180

Question 44

trigonal planar

Answer 44

120

Question 45

tetrahedral

Answer 45

109.5

Question 46

trigonal bipyramidal

Answer 46

120 and 90

Question 47

Octahedral

Answer 47

90

Question 48

molecular geometry

Answer 48

the arrangement of the bonded atoms

Question 49

Nonbonding pairs

Answer 49

are physically larger than bonding pairs, therefore, their repulsions are greater

Question 50

Double and triple bonds

Answer 50

have larger electron domains than single bonds

Question 51

two parts to trigonal bipyramidal

Answer 51

axial, and equatorial

Question 52

lone pairs in trigonal bipyramidal occupy

Answer 52

equatorial positions

Question 53

trigonal bipyramidal electron shapes

Answer 53

seesaw, t shaped, and linear

Question 54

octahedral electron domain shapes

Answer 54

square pyramidal, square planar

Question 55

nonpolar molecule

Answer 55

equal and oppositely directed bond dipoles

Question 56

polar molecule

Answer 56

has dipoles

Question 57

Valence-Bond Theory

Answer 57

electrons of two atoms begin to occupy the same space, called overlap, resulting in a covalent bond

Question 58

Hybrid orbitals

Answer 58

form by “mixing” of atomic orbitals to create new orbitals of equal energy, called degenerate orbitals

Question 59

hybridization

Answer 59

the process of making hybrid orbitals

Question 60

ratio of orbitals to hybrid orbitals

Answer 60

2:1

Question 61

Hypervalent Molecules

Answer 61

The elements that have more than an octet, would require the d orbitals, works for periods 3 and below

Question 62

Sigma bonds are characterized by

Answer 62

head-to-head overlap. cylindrical symmetry of electron density about the internuclear axis.

Question 63

Pi bonds are characterized by

Answer 63

sideways overlap. electron density above and below the internuclear axis.

Question 64

localized electrons

Answer 64

Bonding electrons (σ or π) that are specifically shared between two atoms

Question 65

delocalized electrons

Answer 65

electrons (shared by multiple atoms)

Question 66

Diamagnetism

Answer 66

the result of all electrons in every orbital being spin-paired. These substances are weakly repelled by a magnetic field

Question 67

Paramagnetism

Answer 67

the result of the presence of one or more unpaired electrons in an orbital.

Question 68

Molecular orbitals characteristics

Answer 68

Maximum of two electrons per orbital Electrons in the same orbital have opposite spin Definite energy of orbital Can visualize electron density by a contour diagram

Question 69

Bonding orbitals

Answer 69

are constructive combinations of atomic orbitals

Question 70

Antibonding orbitals

Answer 70

are destructive combinations of atomic orbitals

Question 71

nodal plane

Answer 71

occurs where electron density equals zero

Question 72

sigma (σ) molecular orbitals

Answer 72

when direct overlap of orbitals form a bond

Question 73

energy-level diagram

Answer 73

shows how orbitals from atoms combine to form molecular orbitals

Question 74

Bond order (for MO diagram)

Answer 74

½(# of bonding electrons – # of antibonding electrons) = ½(2 – 0) = 1 bond