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unit 4 Flashcards

1
Q

definition of transition element

A

element with a partially filled d-sublevel or can form a stable cation with an incomplete d-sublevel

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2
Q

what are some properties of transition metals

A
  • high melting points
  • can form alloys
  • magnetic properties
  • variable oxidation states
  • form complex ions
  • form colour complex
  • show catalytic functions
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3
Q

why are changes in properties across d-bloc more subtle than p-block

A

from one element to next, the extra electron goes into the same inner d-sublevel
- d electrons have low effective nuclear charge

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4
Q

charge/radius ratio of transition metals

A

large charge/radius ratio

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5
Q

what happens to melting point from Sc-V

A

melting point increases due to increase in unpaired e <- unpaired e increases electrostatic attraction and metallic bond strength

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6
Q

what happens to melting point from Fe-Cu

A

melting point decreases cus decrease in unpaired e<-decreasing electrostatic attraction and metallic bond strengt

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7
Q

high/low melting point of transition metals. why?

A

high
- strong metallic bonds

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8
Q

high/low malleability and ductility of transition metals. why?

A

high
- metallic bonds (e are not attracted to only one proton <- sea of delocalized e)

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9
Q

high/low density of transition metals. why?

A

high
- small atomic radius

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10
Q

high/low tensile strength of transition metals. why?

A

high
- can hold large loads without breaking

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11
Q

high/low electrical conductivity of transition metals. why?

A

high
- large # of delocalized electrons

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12
Q

how is magnetic field generated in transition metal

A
  • spin motion of an electron about its own axis
  • when electron paired, magnetic properties cancel out
  • some transition metals have electrons remaining unpaired-> magnetic props
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13
Q

diamagnetic meaning

A

materials containing paired electrons showing weak opposition to applied magnetic field
- mostly paired e

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14
Q

paramagnetic meaning

A

substances with unpaired electrons-> magnetism is proportional to applied field and in same direction
- at least 1 unpaired e

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15
Q

what type of magnetism do transition metals typically show

A

paramagnetism - due to unpaired e

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16
Q

what is ferromagnetism

A

occurs when long range ordering of unpaired e creates magnetism that can be greater than applied field

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17
Q

how does ferromagnetism work

A
  • unpaired e line up with parallel spins in regions called domains
  • domains uniformly distributed and become ‘ordered’ when exposed to external magnetic field
  • alignment remains after field is removed
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18
Q

which elements experience ferromagnetism

A

Fe, Co, Ni

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19
Q

oxidation state definition

A

hypothetical charge that an atom in a compound would have if e pairs in bond belonged solely to the more electronegative atom

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20
Q

what is oxidation state used for

A
  • keep track of e being transferred
  • represents charge on an atom in a compound if it were composed of ions
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21
Q

what is the oxidization number

A

positive or negative number corresponding to oxidation state assigned

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22
Q

oxidation state rule 1: pure elements

A
  • pure element = oxidation state 0
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23
Q

oxidation state rule 2: net charge

A
  • sum of oxidation states of all atoms forming molecule/ion adds up to net charge
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24
Q

oxidation state rule 3: group1,2 metals

A
  • in compounds, g1 have oxidation state of +1, g2 have oxidation state of +2
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25
Q

oxidation state rule 4: fluorine

A
  • fluorine always has oxidation state -1
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26
Q

oxidation state rule 5: oxygen atoms

A
  • normally: oxidation state -2
  • oxygen bonded to fluorine: +2
  • peroxides(exH2O2): -1
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27
Q

oxidation state rule 6: hydrogen atoms

A
  • normally: oxidation state +1
  • except when combined with group 1, 2 elements
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28
Q

oxyanions meaning

A
  • polyatomic anions that include oxygen atoms
29
Q

naming oxyanions

A
  • name compound like usual then include oxidation state of non-oxygen atom as roman numeral at end of the name
30
Q

what are variable oxidation states

A
  • the ability to form a variety of stable ions in different oxidation states
31
Q

trend of oxidation states in transition metals

A
  • Sc-Mn most stable oxidation state is the highest possible one
  • Fe-Cu most stable oxidation state is 2+
32
Q

what oxidation state can all transition metals have, why?

A

+2, because 4s electrons are removed first

33
Q

what is werner’s theory

A
  • that certain metal atoms (mainly transition) have 2 types of valence
  • valence 1: oxidation number for the metal
  • valence 2: coordination number<- the number of atoms directly bonded to metal
34
Q

how are complex ions formed

A
  • ions of d-block elements attract species that are rich in electrons(ligands) because of small size and high charge density
  • forms coordinate covalent bonds
35
Q

ligand definition

A

a neutral molecule or anion which contains a nonbonding pair of elections and is able of donating electron pairs to central ion

36
Q

what is a monodentate ligand

A

when ligand has only one donor atom/electron
- may be neutral molecule or negatively charge ion

37
Q

what is a polydentate ligand

A

when a ligand has two or more donor atoms
- ex. bidentate ligands for 2 binds to central atom <- takes up 2 bonding spaces

38
Q

coordination number definition

A

number of ligands that can bond with the central mtal ion

39
Q

importance of coordination numbers

A
  • explains the fact that complex ions possess distinctive geometrical shapes called the coordination sphere
40
Q

what are the most common shapes for complex ions

A

linear, square planar, tetrahedral, octahedral

41
Q

how to find coordination number

A

add up subscripts inside square brackets except for central metal atom

42
Q

what does square brackets mean in complex ion formulas

A

the coordinate sphere

43
Q

what is the metal outside of the square brackets called

A

counter ion

44
Q

what is a chelate

A

an organic compound formed when a polydentate ligand bonds to a central metal atom

45
Q

chelation meaning

A

the formation of 2 or more separate coordinate bonds b/w ligand and central atom

46
Q

what other names are given to ligands

A

chelating agents, chelators, chelants, sequestering agents

47
Q

what are the uses of chelates/chelation

A
  • chelation therapy
  • formulates nutritional supplements
  • food additive
  • water softening
  • anticoagulant in blood collection tubes
48
Q

how does chelation therapy work

A

used to treat metal poisoning particularly lead by binding to it so it causes less harm and allowing it to be excreted

49
Q

how does chelation in nutritional supplements work

A
  • chelation protects metal supplements from forming complexes with insoluble salts in stomach <- provides higher capacity for absorption
50
Q

crystal field theory

A

describe the breaking of orbital degeneracy (of d orbitals) in transition metal complexes due to presence of ligands

51
Q

when does repulsion occur in complex ions

A

when a ligand lone pair approaches an occupied metal d orbital
- direct collision b/w e of metal and ligand <- both neg

52
Q

how does the splitting of the d orbital create colour

A
  • energy difference b/w levels corresponds to specific frequency and wavelength in visible spectrum
  • energy difference corresponds to energy absorbed
  • amount of energy absorbed determines visible colour
53
Q

when a wavelength is absorbed, what colour do we see

A
  • wavelength absorbed corresponds to absorbed colour
  • the complimentary colour (across from absorbed colour) is the visible one
54
Q

what do coloured complexes depend on

A
  • size and type of ligand
  • nuclear charge and identity of central metal ion
  • oxidation state
  • shape(geometry) of complex ion
55
Q

how does size/type of ligand affect coloured complexes

A
  • greater ligand charge density, greater interaction w metal ion->greater splitting->the higher the energy absorbed
56
Q

how does nuclear charge and identity of the central metal ion affect colour complexes

A
  • higher nuclear charge=stronger interactions with ligand->greater energy separation b/w orbitals
57
Q

how does oxidation state affect colour complexes

A
  • same metal at higher oxidation state will create stronger interaction with ligands
  • stronger the interaction, greater the energy difference
58
Q

how does shape(geometry) affect colour complexes

A
  • splitting of energy in d orbitals depend on relative orientation of ligand and d orbitals
  • coordination number, which affects shape, affects colour of complex ions
59
Q

why are there colourless complexes

A
  • if the d sublevel is completely empty or completely full, no transitions within the d sublevel can take place<-no colour
60
Q

catalyst definition

A

catalysts increase the rate of a chemical reaction by providing an alternative reaction pathway requiring less energy

61
Q

heterogeneous vs homogeneous catalysts

A

catalyst of different state than reactants vs. catalyst of same state as reactants

62
Q

how are catalysts used in haber process

A
  • catalyst: Fe
  • used in production of ammonia for fertilizers, drugs
63
Q

how are catalysts used in contact process

A
  • catalyst: V2O5
  • used in production of sulfur trioxide to manufacture sulfuric acid
64
Q

how is Ni used as a catalyst

A
  • used in conversions of alkenes to alkanes
  • commonly used for conversion of vegetable oils to margarine
65
Q

how are Pd and Pt used as catalysts

A

helps remove harmful pollutants like NOx to allow for more efficient complete combustion

66
Q

how is MnO2 used as a catalyst

A
  • used in decomposition of hydrogen peroxide and organic compounds via oxidation
67
Q

how Fe2+ used as a catalyst in blood (heme complex)

A
  • heme complex has coord # of 6
  • 4 sites bound to N of porphyrin ring
  • 1 site bound to N from protein chain
  • 6th position can be filled with O2 molecule
  • each hemoglobin can carry 4 O2 molecules
  • water can occupy O2’s space when it’s released
68
Q

heme complex in myoglobin and hemoglobin

A
  • myoglobin contains 1 heme complex (carry 1 O2 molecule) while hemoglobin contains 4 myoglobin - 4 heme complex (carry 4 O2 molecule)

hl chemistry (7 decks)

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