Ch 2 Chemical Bonding and Lewis Structure

Question 1

compound

Answer 1

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

Question 2

anion

Answer 2

species possessing overall negative charge

non isolable

Question 3

cation

Answer 3

species possessing overall positive charge

non isolable

Question 4

diff names for ions containing multiple atoms

Answer 4

complex ions, polyatomic ions, molecular ions

Question 5

ionic bonds

Answer 5

opp charged ions held tgth by electrostatic forces

Question 6

trend in electronegativity

Answer 6

higher negativity towards fluorine, most electronegative

Question 7

covalent bonds

Answer 7

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

Question 8

metallic bonds

Answer 8

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

Question 9

what electronegativity difference leads to ionic vs covalent

Answer 9

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

Question 10

relationship between trends in electronegativity and atomic radius etc

Answer 10

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

Question 11

electron affinity

Answer 11

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

Question 12

ionization energy

Answer 12

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

Question 13

homonuclear diatomic species

Answer 13

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

Question 14

molecules containing non polar covalent bonds

Answer 14

homonuclear diatomic species

Question 15

polar covalent bonds

Answer 15

electrons polarized towards atom ^ electronegativity

Question 16

ionic compounds

Answer 16

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

Question 17

common rxn group 1 and group 17

Answer 17

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

Question 18

redox reaction

Answer 18

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

Question 19

closed shell

Answer 19

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

Question 20

octet

Answer 20

closed valence shell w 8 electrons

Question 21

bond order

Answer 21

bonds between atoms

Question 22

bond length

Answer 22

distance between two nuclei participating in bond

Question 23

bond dissociation energy

Answer 23

energy needed to completely seperate bonded atoms

Question 24

relationship bond order, length, dissociation energy

Answer 24

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

Question 25

heteronuclear diatomic molecule

Answer 25

electrons not shared equally, polar

Question 26

bond dipole

Answer 26

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

Question 27

how to rep bond dipoles

Answer 27

delta plus or minus and arrow with cross on tail

Question 28

percent ionic character definition and how to calculate

Answer 28

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

Question 29

what % ionic character ionic?

Answer 29

more than 50% ionic character ionic

Question 30

importance of arrangement of atoms and bonds

Answer 30

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

Question 31

octet rule

Answer 31

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

Question 32

name atoms incomplete octet

Answer 32

electron deficient

Question 33

importance electron deficient compounds

Answer 33

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

Question 34

name of atoms greater than 8 valence electrons

Answer 34

hypervalent, or expanded octet

Question 35

unpaired electrons, name and importance

Answer 35

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

Question 36

nitric oxide

Answer 36

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

Question 37

formal charge

Answer 37

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

Question 38

steps to drawing lewis structures

Answer 38

1. arrange symbols, least electronegative in center 2. add valence electrons 3.draw single bonds 4. anions, add electrons most electronegative terminal. cations, remove electrons central atom 5. additional bonds unpaired electrons 6. rearrange for octets 7. redraw 8. label formal charges 9. check electron count 10. determine which one is best structure if multiple options

Question 39

how to determine if best lewis structure

Answer 39

1. formal charges minimized 2. neg formal charges on more electronegative atoms

Question 40

arrow heads when drawing atomic movement resonance structures

Answer 40

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

Question 41

resonance structures

Answer 41

multiple structures, same position atoms but different arrangement of electrons

Question 42

true structure and resonance

Answer 42

true structure is weighted average of set of resonance

Question 43

how to draw resonance structures

Answer 43

double headed arrow between

Question 44

valid resonance structure

Answer 44

octet rule is satisfied on all atoms

Question 45

best resonance structure

Answer 45

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

Question 46

chemically reasonable res structure

Answer 46

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

Question 47

what element doesn't do double bonds

Answer 47

fluorine

Question 48

what do resonance structures actually mean?

Answer 48

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

Question 49

isomers

Answer 49

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

Question 50

resonance curvey arrow notation

Answer 50

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

Question 51

drawing lewis with more than one central atom

Answer 51

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

Question 52

general rules/characteristics lewis structures

Answer 52

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

Question 53

oxidation state

Answer 53

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

Question 54

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

Answer 54

NEITHER!!!! true charge distribution somewhere between two extremes partial charge probably better

Question 55

partial charge

Answer 55

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

Question 56

bronsted-lowry acids and bases

Answer 56

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

Question 57

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

Answer 57

partial charge NOT formal

Question 58

common acid in acid base reactions

Answer 58

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

Question 59

Li+ etc how many valence electrons?

Answer 59

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