Chapter 2: Chemical Bonding and Lewis Structures Flashcards
1
Q
compounds (2)
A
- chemicals that are combinations of 2 or more different elements in defined properties
- do not have overall charges (“charge neutral”)
2
Q
ions (2)
A
- species possessing an overall negative charge or overall positive charge
- cannot be isolated, (they are insoluble) in their condensed phases (liquid, solid) without ion of opposite charge present to balance the charge to form a net-neutral compound
3
Q
anion
A
- ions carrying an overall negative charge
4
Q
cation
A
- ions carrying an overall positive charge
5
Q
simple ions
A
- ions that contain a single atom
6
Q
complex ions (2)
A
- ions that contain multiple atoms
- aka polyatomic atoms or molecular atoms
7
Q
purpose of forming bonds
A
- elements achieve a lower overall energy than they would in their free elemental form
8
Q
ionic bonds
A
- occur when oppositely charged ions are help together by electrostatic forces
9
Q
covalent bonds
A
- occur when atoms are held together by mutual attraction of a pair (or pairs) of electrons to the nuclei in adjacent atoms, the electrons are “shared” between atoms
10
Q
metallic bonds (2)
A
- occur when electrons are shared between many atoms simultaneously and are free to “flow” between atoms
- in elemental metals or metallic alloys (mixture of two or more elemental metals), this bond is the most important
11
Q
electronegativity (2)
A
- tendency of an atom in a molecule to attract electrons to itself
- cannot be discussed unless it is apart of a molecule or molecular ion
12
Q
polar covalent bonds
A
- electrons are polarized towards the atom with greater electronegativity, so the electrons are shared unequally
13
Q
bond polarity (2)
A
- measured by the subtraction of the lesser electronegativity from the greater electronegativity
- bonds with high differences in electronegativity can be considered to be ionic
14
Q
ionic compounds (4)
A
- commonly referred to as salts
- consist of ions held together with electrostatic forces
- when melted, cations and anions move past each other freely and resulting liquid conducts electricity
- can carry a charge from one place to another, motion of charged ions result in an electric current
15
Q
can covalent compounds conduct electricity in a liquid state?
A
- they do not conduct electricity as there are no ions present after melting, covalent bonds remain intact during phase changes
16
Q
how do the alkali metals (group 1) and alkaline earth metals react (group 2) in ionic compounds
A
- group 1 metals are found as M+ ions in ionic compounds
- group 2 metals are found as M2+ ions in ionic compounds
17
Q
redox reaction (2)
A
- total number of electrons lost must be equal to the total number of electrons gained
- in a reaction between an alkali metal atom and a halogen atom the electron is formally transferred from the alkali to the halogen: the alkali metal is oxidized and the halogen is reduced
18
Q
covalent bond (2)
A
- exists when a pair of electrons is shared between 2 atoms
- pair of electrons is called a bond pair, valence electrons that do not participate are called lone pair
19
Q
bond order
A
- number of bond pairs between two atoms
20
Q
bond length
A
- distance between 2 nuclei participating in a bond
21
Q
bond dissociation energy
A
- determines strength of a bond, experimental value describing how much energy needs to be added to break a particular bond
22
Q
describe the trend between bond order, length and dissociation energy
A
- smaller bond order: larger bond length and smaller dissociation energy
23
Q
bond dipole (2)
A
- result of electrons being polarized towards the atom with greater electronegativity
- one atom will have a partial positive charge and the other will have a partial negative charge
24
Q
what symbol is used to indicate a bond dipole
A
- arrow with a crossed tail is used to indicate the direction of a bond dipole (points towards excess negative charge)
25
Q
how do you measure percent character of a bond
A
- ratio of the actual bond dipole to the bond dipole if the bond was purely ionic
26
Q
octet rule
A
- atom satisfy this rule is they have 8 valence electrons, achieved by forming covalent bonds
27
Q
how do you determine whether an atom has a complete octet?
A
- count the lone pair electrons on the atom
- count all bonding electrons (twice the number of bonds to the atom)
- octet rule is satisfied if #1 and #2 have a complete octet
28
Q
“electron deficient” compounds (2)
A
- group 13 elements only have 3 valence electrons in their outer shell and can achieve a maximum of six valence electrons
- these compounds do not have to conform to octet rule as they are unable to achieve a complete octet
29
Q
hypervalent species (3)
A
- species containing elements in the third or later periods of the p-block may have more than an octet of electrons
- central atom has an expanded octet
- “central atom with more electrons in its valence shell then predicted in the octet rule”
30
Q
free radicals
A
- species that contain unpaired electrons
31
Q
formal charge
A
- determined by imagining bonding electrons are shared exactly equally between atoms and occurs when bonded atom has a greater or fewer number of electrons than its free form
32
Q
what is the procedure for drawing valid lewis structures for species with one central atom
A
- arrange atom symbols
- add valence electrons
- draw bonds
- rearrange electrons for octet and check octet rule
- label formal charges
- check electron count
33
Q
when do resonance structures exist? (2)
A
- when two are more Lewis structures can represent the arrangement of electrons in the same molecule or molecular ion
- positions and connectivity of the atomic nuclei are identical
34
Q
valid resonance structures
A
- any structure where the octet rule is satisfied on all atoms (other than known exceptions)
35
Q
best resonance structures
A
- a structure that has minimal formal charges and has negative formal charges on more electronegative elements
36
Q
chemically reasonable resonance structure (2)
A
- any valid resonance structure where the magnitudes of the formal charges are small
- represent bonding that is typical of various elements
37
Q
isomers
A
- chemical species that have the same molecular formula, but a different arrangement of atoms, not to be confused with resonance structures
38
Q
acid-base theory
A
- the acid is the proton (H+) donor and the base is the proton acceptor
