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unit 4 Flashcards

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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
oxidation state rule 4: fluorine
- fluorine always has oxidation state -1
26
oxidation state rule 5: oxygen atoms
- normally: oxidation state -2 - oxygen bonded to fluorine: +2 - peroxides(exH2O2): -1
27
oxidation state rule 6: hydrogen atoms
- normally: oxidation state +1 - except when combined with group 1, 2 elements
28
oxyanions meaning
- polyatomic anions that include oxygen atoms
29
naming oxyanions
- name compound like usual then include oxidation state of non-oxygen atom as roman numeral at end of the name
30
what are variable oxidation states
- the ability to form a variety of stable ions in different oxidation states
31
trend of oxidation states in transition metals
- Sc-Mn most stable oxidation state is the highest possible one - Fe-Cu most stable oxidation state is 2+
32
what oxidation state can all transition metals have, why?
+2, because 4s electrons are removed first
33
what is werner's theory
- 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
how are complex ions formed
- 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
ligand definition
a neutral molecule or anion which contains a nonbonding pair of elections and is able of donating electron pairs to central ion
36
what is a monodentate ligand
when ligand has only one donor atom/electron - may be neutral molecule or negatively charge ion
37
what is a polydentate ligand
when a ligand has two or more donor atoms - ex. bidentate ligands for 2 binds to central atom <- takes up 2 bonding spaces
38
coordination number definition
number of ligands that can bond with the central mtal ion
39
importance of coordination numbers
- explains the fact that complex ions possess distinctive geometrical shapes called the coordination sphere
40
what are the most common shapes for complex ions
linear, square planar, tetrahedral, octahedral
41
how to find coordination number
add up subscripts inside square brackets except for central metal atom
42
what does square brackets mean in complex ion formulas
the coordinate sphere
43
what is the metal outside of the square brackets called
counter ion
44
what is a chelate
an organic compound formed when a polydentate ligand bonds to a central metal atom
45
chelation meaning
the formation of 2 or more separate coordinate bonds b/w ligand and central atom
46
what other names are given to ligands
chelating agents, chelators, chelants, sequestering agents
47
what are the uses of chelates/chelation
- chelation therapy - formulates nutritional supplements - food additive - water softening - anticoagulant in blood collection tubes
48
how does chelation therapy work
used to treat metal poisoning particularly lead by binding to it so it causes less harm and allowing it to be excreted
49
how does chelation in nutritional supplements work
- chelation protects metal supplements from forming complexes with insoluble salts in stomach <- provides higher capacity for absorption
50
crystal field theory
describe the breaking of orbital degeneracy (of d orbitals) in transition metal complexes due to presence of ligands
51
when does repulsion occur in complex ions
when a ligand lone pair approaches an occupied metal d orbital - direct collision b/w e of metal and ligand <- both neg
52
how does the splitting of the d orbital create colour
- 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
when a wavelength is absorbed, what colour do we see
- wavelength absorbed corresponds to absorbed colour - the complimentary colour (across from absorbed colour) is the visible one
54
what do coloured complexes depend on
- size and type of ligand - nuclear charge and identity of central metal ion - oxidation state - shape(geometry) of complex ion
55
how does size/type of ligand affect coloured complexes
- greater ligand charge density, greater interaction w metal ion->greater splitting->the higher the energy absorbed
56
how does nuclear charge and identity of the central metal ion affect colour complexes
- higher nuclear charge=stronger interactions with ligand->greater energy separation b/w orbitals
57
how does oxidation state affect colour complexes
- same metal at higher oxidation state will create stronger interaction with ligands - stronger the interaction, greater the energy difference
58
how does shape(geometry) affect colour complexes
- 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
why are there colourless complexes
- if the d sublevel is completely empty or completely full, no transitions within the d sublevel can take place<-no colour
60
catalyst definition
catalysts increase the rate of a chemical reaction by providing an alternative reaction pathway requiring less energy
61
heterogeneous vs homogeneous catalysts
catalyst of different state than reactants vs. catalyst of same state as reactants
62
how are catalysts used in haber process
- catalyst: Fe - used in production of ammonia for fertilizers, drugs
63
how are catalysts used in contact process
- catalyst: V2O5 - used in production of sulfur trioxide to manufacture sulfuric acid
64
how is Ni used as a catalyst
- used in conversions of alkenes to alkanes - commonly used for conversion of vegetable oils to margarine
65
how are Pd and Pt used as catalysts
helps remove harmful pollutants like NOx to allow for more efficient complete combustion
66
how is MnO2 used as a catalyst
- used in decomposition of hydrogen peroxide and organic compounds via oxidation
67
how Fe2+ used as a catalyst in blood (heme complex)
- 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
heme complex in myoglobin and hemoglobin
- myoglobin contains 1 heme complex (carry 1 O2 molecule) while hemoglobin contains 4 myoglobin - 4 heme complex (carry 4 O2 molecule)
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