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IB Chemistry > periodicity– transition metals > Flashcards

periodicity– transition metals Flashcards

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1
Q

what are transition metals? (short defin.)

A
  • a d-block element that forms 1 or more stable ions w partially filled d subshell
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2
Q

what are the exceptions in the transition metals?

A

Zn, Sc3+, Cu+

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3
Q

why is Zn not considered a transition metal?

A
  • it forms only 1 ion, Zn2+
  • Zn2+ has a fully filled d subshell
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4
Q

why is Sc3+ not considered a transition metal?

A

it has no e- in its d subshell

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5
Q

why is Cu+ not a transition metal?

A

it has a fully filed d subshell

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6
Q

____ orbitals are filled before ___

A

4s, 3d

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7
Q

in transition metals, 4s is filled before 3d except for…

A

Cr and Cu

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8
Q

why do Cr and Cu not have a fully filled 4s orbital?

A
  • Cr -> 3d orbitals are half filled and more stable than fully filled 4s
  • Cu -> 3d orbitals are fully filled and stable
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9
Q

d-block metals have a [higher/lower] m.p. compared to s-block metals

A

higher

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10
Q

is the atomic radii of transition metals generally larger or smaller than s-block metals?

A

smaller

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11
Q

transition metals are [more/less] dense than s-block metals

A

more

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12
Q

_____ metals are poorer conductors of electricity compared to ______ metals

A

s-block, d-block

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13
Q

why is the atomic and ionic radii of d-block elements smaller than s-block elements?

A
  • d subshell SE not as effective as p subshell
    • as d subshells are more diffused
  • valence shell for d-block elements exp greater nuclear attraction -> smaller radii
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14
Q

how does the atomic radius change across the period and why?

A
  • decr slightly:
    • due to nuclear charge incr slightly -> SE incr slightly -> ENC increases slightly
    • thus radius decr slightly
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15
Q

what is the trend for ionisation energies across the period?

A
  • incr slightly
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16
Q

why does ionisation energies incr slightly from s-block to d-block

A
  • p subshell provides better shielding than d subshell
    • d subshells more diffused
  • valence shell of d-block elements exp greater nuclear attraction
  • thus greater IE for d-block
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17
Q

there is a ______ incr from 1st to 2nd IE, and a _______ incr from 2nd to 3rd IE

A

small, large

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18
Q

there is a small incr from 1st to 2nd IE because…

A

both first and second electrons are removed from the same orbital, 4s

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19
Q

the large increase from 2nd to 3rd IE in d block elements is because…

A
  • third electron is removed from 3d subshells
  • SE decr -> ENC incr
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20
Q

why is the 2nd IE of Mn lower than that of Cr?

A
  • 2nd e- removed from Mn is 4s
  • 2nd e- removed from Cr is 3d
  • 4s is in outer shell -> experiences weaker ENC
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21
Q

why is the 3rd IE of Mn>Fe?

A
  • Fe = 3d6
  • electron removed is in the same orbital as another electron
    • inter-electronic repulsion
  • thus less energy req
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22
Q

why do trans elements have greater m.p. than s-block?

A
  • 3d + 4s energies are relatively similar
    • TM can lose more valence e-
    • thus more delocalised e-
  • stronger electrostatic FOA btw metal cation and sea of delocalised e-
  • TMS have stronger metallic bonding -> higher m.p.
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23
Q

what is the trend of m.p. across the d-block?

A

incr then decr

24
Q

why does m.p. increase from Sc to Cr?

A
  • Cr has 5 unpaired e- (3d)
  • Sc has 1 unpaired e- (3d)
  • Cr has more unpaired e- in 3d subshell
  • thus stronger metallic bonding
25
Q

why does m.p. decrease from Fe to Zn?

A
  • less unpaired e- in 3d subshell
  • weaker metallic bonding
26
Q

why are d-block elements more dense than s-block

A
  • stronger metallic bond strength
  • smaller atomic radii
    thus more closely packed
27
Q

why does Mn have a lower m.p.?

A

Cr: 4s1 3d5
Mn: 4s2 3d5
- Mr has less unpaired e-
- thus weaker metallic bonds
- lower m.p.

28
Q

the density of d-block elements ______ across the period as…

A

incr
- atomic radii decr slightly
- more atoms can be packed closely together

29
Q

what are the two forms of magnetism?

A

paramagnetism, diamagnetism

30
Q

paramagnetism is when..

A

an ion, molecule, atom has unpaired e-

31
Q

paramagnetic substances are [attracted/repelled] by a magnetic field, as…

A

attracted
- unpaired e- give rise to a magnetic field that can be affected by external magnetic field

32
Q

diamagnetism is caused by ______ e-.

A

paired

33
Q

how do diamagnetic substances respond to a magnetic field?

A

they are repelled

34
Q

how do you find the maximum oxidation state of a TM?

A

no. 4s e- + no. 4d e-

35
Q

what is a catalyst?

A

a substance that incr the ROR by providing an alternative rxn pathway that lowers Ea

36
Q

what are the two types of catalysts?

A
  • homogenous
  • heterogenous
37
Q

heterogenous catalysts are in a ______ ________ as the reactants

A

diff phase

38
Q

how do TMs act as heterogenous catalysts? (3)

A
  1. reactants adsorb to e active sites of catalyst
    • weakens the covalent bonds within the rxt molecules
    • lowers Ea for the rxn
  2. it incr surface conc and ensures proper orientation for the rxn
  3. products deabsorb fr e active site -> freeing up active sites
39
Q

why can TMs act as homogenous catalysts? (1)

A
  • they can form variable oxidation states
    • i.e. they can be easily converted fr one ox state to another
40
Q

what are ligands? (defin.)

A

an anion or molecule that has at least one lone pair of e- that can be donated into the vacant orbitals in the central metal atom

41
Q

what are complexes? (defin.)

A

a complex consists of a central metal atom or ion surrounded by other ions or molecules called ligands through dative bonds

42
Q

ligands act as _______

A

Lewis bases

43
Q

why can TMs form complexes? (2)

A

their metal cations have
1. high charge densities
- hence high polarising power -> cations can attract lone pair of e- from ligands
2. vacant, low-lying 3d orbitals
- can accept lone pair of e- donated by ligands -> dative bond formed

44
Q

ligands can be _________ charged or ___________ charged

A

neutrally or negatively

45
Q

why are ligands Lewis bases?

A

they are e- pair donors

46
Q

a ligand that forms 2 dative bonds is called…

A

bidentate

47
Q

what is ligand exchange?

A

a stronger ligand replacing a weaker ligand from a cation complex

48
Q

ligand exchange can be seen through observing a _______________

A

colour change

49
Q

why are TM complexes coloured? (short)

A

due to the presence of partially filled d-orbitals

50
Q

why are some TM complexes colourless?

A
  • complexes with Sc3+ ion -> 3d subshell is empty
  • Zn2+ -> 3d subshell is full
51
Q

why do transition metals form coloured compounds? (4)

A
  • in the presence of ligands, the d orbital splits into 2 energy levels
  • an e- in the lower energy level is able to be promoted to the higher energy level
  • by absorbing a wavelength of light in the visible region
  • the complimentary colour of the light absorbed is observed
52
Q

what affects the colour of complexes? (2)

A
  1. nature and oxidation state of TM
  2. nature of ligands
53
Q

how does the nature and oxidation state of TM affect the colour of complexes?

A
  • diff no. of e- in the d orbitals repel e- of ligands to a diff extent
  • gives rise to diff energy gaps -> diff colour
54
Q

the nature of ligands affects the colours of complexes as…

A

diff ligands split the d-orbitals to a diff extent

55
Q

the longest wavelength is…

A

red

56
Q

what is the shortest wavelength?

A

violet

IB Chemistry (12 decks)

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