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Chem 121 💅🧪👩‍🔬 > Ch 2 Chemical Bonding and Lewis Structure > Flashcards

Ch 2 Chemical Bonding and Lewis Structure Flashcards

1
Q

compound

A

combinations of two or more diff elements in defined proportions, no overall changers

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2
Q

anion

A

species possessing overall negative charge

non isolable

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3
Q

cation

A

species possessing overall positive charge

non isolable

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4
Q

diff names for ions containing multiple atoms

A

complex ions, polyatomic ions, molecular ions

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5
Q

ionic bonds

A

opp charged ions held tgth by electrostatic forces

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6
Q

trend in electronegativity

A

higher negativity towards fluorine, most electronegative

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7
Q

covalent bonds

A

mutual attraction of a pair of electrons to nuclei or adjacent atoms, shared electrons

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8
Q

metallic bonds

A

electrons shared simultaneously atoms, flow, elemental metals or metal alloys - metallic bonds

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9
Q

what electronegativity difference leads to ionic vs covalent

A

0>x - 0.4 slightly polar, 0.5 - 2.0 polar, 2.1< ionic

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10
Q

relationship between trends in electronegativity and atomic radius etc

A

higher electronegativity up table as atomic radius decreases, therefore electrons held more tightly to nucleus and ^ attraction

electron affinity, ionization energy increases along with electronegativity

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11
Q

electron affinity

A

energy released when electron added to neutral atom to form neg charged ion

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12
Q

ionization energy

A

energy required to remove most loosely bound electron of an isolated, gaseous atom, positive ion, or molecule

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13
Q

homonuclear diatomic species

A

molecules containing non polar covalent bonds, atoms in the bond have same electronegativity

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14
Q

molecules containing non polar covalent bonds

A

homonuclear diatomic species

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15
Q

polar covalent bonds

A

electrons polarized towards atom ^ electronegativity

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16
Q

ionic compounds

A

ions held together w/ electrostatic forces, when melted, conduct electricity due to freely moving anions and cations

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17
Q

common rxn group 1 and group 17

A

alkali metals x halogens (17) - alkali metal halides, one electron transferred alkali metal atom to halogen

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18
Q

redox reaction

A

reduction-oxidation, oxidized - loses an electron, reduced - gain an electron, total elec lost = total gained

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19
Q

closed shell

A

atom has same # electrons valence shell as noble gas in the same row, generally 8, full valence shell

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20
Q

octet

A

closed valence shell w 8 electrons

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21
Q

bond order

A

bonds between atoms

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22
Q

bond length

A

distance between two nuclei participating in bond

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23
Q

bond dissociation energy

A

energy needed to completely seperate bonded atoms

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24
Q

relationship bond order, length, dissociation energy

A

higher bond order, shorter bond length, higher bond dissociation energy

25
Q

heteronuclear diatomic molecule

A

electrons not shared equally, polar

26
Q

bond dipole

A

unequal distribution of electrons, partial positive and partial negative charge (delta plus or minus)

27
Q

how to rep bond dipoles

A

delta plus or minus and arrow with cross on tail

28
Q

percent ionic character definition and how to calculate

A

ratio of actual bond dipole (measured) to calculated bond dipole if the pair purely ionic

% ionic character = (measured dipole moment X-Y / calculated dipole momend of X+Y-) x 100

29
Q

what % ionic character ionic?

A

more than 50% ionic character ionic

30
Q

importance of arrangement of atoms and bonds

A

allows us to predict physical properties and chemical reactivity of different chem compounds

31
Q

octet rule

A

want 8 electrons in valence shell, if period 3 or higher can possible expand octet IF reduces formal charge

some elements group 13 can have just 6 valence electrons

32
Q

name atoms incomplete octet

A

electron deficient

33
Q

importance electron deficient compounds

A

elec deficient comp of carbon, key in many reactions of organic chem. Ex tertiary butyl cation important intermediate in industrial production of rubber (polyisobutylene)

34
Q

name of atoms greater than 8 valence electrons

A

hypervalent, or expanded octet

35
Q

unpaired electrons, name and importance

A

free radicals, messenger molecules in living systems and reactive species in atmospheric chemistry

36
Q

nitric oxide

A

molecule of the year 1992, signalling molecule, penetrate cell walls and trigger relaxation of vascular smooth muscle, blood vessel dilation, and increased blood flow

37
Q

formal charge

A

difference between number of valence electrons unbonded atom and # in bonded. each bond pair counted as one electron

indicated with little charge + 1 2+ 2- with little circle around it right next to the atom

38
Q

steps to drawing lewis structures

A
  1. arrange symbols, least electronegative in center
  2. add valence electrons

3.draw single bonds

  1. anions, add electrons most electronegative terminal. cations, remove electrons central atom
  2. additional bonds unpaired electrons
  3. rearrange for octets
  4. redraw
  5. label formal charges
  6. check electron count
  7. determine which one is best structure if multiple options
39
Q

how to determine if best lewis structure

A
  1. formal charges minimized
  2. neg formal charges on more electronegative atoms
40
Q

arrow heads when drawing atomic movement resonance structures

A

half arrow head one electron, full head two electrons of bond

41
Q

resonance structures

A

multiple structures, same position atoms but different arrangement of electrons

42
Q

true structure and resonance

A

true structure is weighted average of set of resonance

43
Q

how to draw resonance structures

A

double headed arrow between

44
Q

valid resonance structure

A

octet rule is satisfied on all atoms

45
Q

best resonance structure

A

minimal formal charge, neg formal charge on more electronegative elements, positive on less, this is lowest energy configuration

46
Q

chemically reasonable res structure

A

any valid resonance where magnitude formal charge small (but not necessarily minimized) represent bonding typical of various elements

47
Q

what element doesn’t do double bonds

A

fluorine

48
Q

what do resonance structures actually mean?

A

true structure would be a hybrid of all but thats hard to show, so resonance structures none of them are really the true structure

49
Q

isomers

A

isomers same molecular formula DIFF arrangement of atoms (resonance same arrangement atoms, diff electrons)

50
Q

resonance curvey arrow notation

A

1st res structure with arrows pointing to where electron pairs/bonds would move to in second

Arrow Pushing

51
Q

drawing lewis with more than one central atom

A

pay close attention to # of electrons, probable lots resonance structures

52
Q

general rules/characteristics lewis structures

A

all valence shown, all electrons assigned, octet rule, minimal formal charge, neg formal charge on most electroneg, actual molecular structure hybrid of all structures

53
Q

oxidation state

A

measure of degree of electron loss of an atom in chem species.

IONIC COMPOUND - same as charge on ionic form

COVALENT BONDS - charge the atom would have after bonding electrons “given” to more electronegative atom

54
Q

does formal charge or oxidation state describe electron distribution better covalent bonds?

A

NEITHER!!!! true charge distribution somewhere between two extremes

partial charge probably better

55
Q

partial charge

A

bonds aren’t really purely ionic or covalent, have dipoles rep by partial positive or partial neg charge (delta + or -), magnitude of partial charge, difference in electronegativity

probably best representation of true charge distribution

56
Q

bronsted-lowry acids and bases

A

acid is a proton donor (H+), base proton acceptor

57
Q

what sort of charge should you look at to determine what sort of reaction occurs (acid base)

A

partial charge NOT formal

58
Q

common acid in acid base reactions

A

hydronium ion (H3O+), bonding electrons between one of the H and O move to O creating H2O, Proton H+ move to base (ex ammonia) form bond using 2 electrons from the base

59
Q

Li+ etc how many valence electrons?

A

base it on the highest occupied shell of non ionized form , so for Li+ it would be 0

Chem 121 💅🧪👩‍🔬 (14 decks)

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