d & f block Flashcards
Why is ns^0-2 written in d orbital valence shell electronic config?
Since Pd has 0 e`s in S orbital
What are transition elements?
Those which have incompletely filled d-orbitals in ground and excited (oxidation) state
Why are Zn, Cd & Hg not transition metals?
They have completely filled d-orbitals even after losing e’s from s orbital
Zn & Hf occur together in nature. Why?
Due to same properties like atomic size
All groups have metal behavious except for
group 12
When no of unpaired e’s are more, bonding in metal
increases
Down the group, atomisation enthalpy
increases
what is enthalpy of atomization?
Energy needed to break the bond to atoms
Why does atomic size decrease and gradually increase again across the period?
Due to shielding effect, nucleus is not able ot hold all e’s
What is lanthanoid contraction?
gradual decrease in the atomic and ionic size of lanthanoids with an increase in atomic number
Why is lanthanoid contraction seen in 5d & 6s series & 4d and 5d series?
14 e’s offer poor shielding effect from the element Hf which causes decrease in atomic size
Why does density of 3d elements increase from Sc to Zn?
Atomic mass increases
Why is ionisation enthalpy for 3d series irregular?
Due to irregularity in atomic size, it is lower for Cr due to absence of change in config while Zn has change in 4s config. b
If reduction potential is high, its stabitlity is
less in aq solution
Why is Cu1+ less stable than Cu2+?
Cu1+ has greater reduction potential and Cu2+ is surrounded by many water molecules due to which hydration enthalpy increases so it is stable
What happens when Cu+ is present in aq. sol?
It undergoes oxidation & reduction at the same time called disproportionation rn.
Why does Cu have +ve potential?
2nd ionisation enthalpy is very high due to which sum of enthalpies is +ve
Why does Mn show a less tendency to get reduced?
After losing 2 e’s, it has stable half filled d orbital and -ve potential
If potential is +ve, it will show more tendency to
get reduced
Ni has -ve potential due to
high hydration enthalpy
why is there irregularity in potentials?
Due to irregularity in sublimation & ionisation enthalpies
The stability of divalent ions decrease. Why?
Since the potentials are becoming less -ve across the period.
Why is Mn2+ resistant to oxidation but Fe2+ is not?
Due to half filled orbitals in Mn2+
Why is reduction potential of Mn3+ high?
It is easy for Mn3+ to gain 1 e’ to be stable
Co3+ & Mn3+ are ________ agents
oxidising
Ti2+, Cr2+ & V2+ are __________ agents
reducing
Which elements doesn’t react with dilute acids at room temp?
Ti & V
Why Cu will not react with acid to liberate H2?
It has +ve potential
Which only shows +1 state?
Cu
Which shows max oxidation states?
Mn
Why transition elements show variable oxidation states?
(n-1)d and ns e’s are involved in bond formation, pairing of e’s takes place
Why does Mn show many oxidation states?
Due to 5 unpaired e’s in ‘d’ & 2 in ‘s’
Commonly seen oxidation state in group 15 elements
+3 & +5
Why does +3 stability increase down the group?
Due to inert pair effect where nucleus holds e’s in s orbitals which causes increase in nuclear charge & reluctance in bond formation of e’s
Which oxidation state is stable for p block?
lower
Which oxidation state is stable for d block?
higher
For Mo & W, which is stable?
+6
Why does K2Cr2O7 act as good oxidising agent?
Since it is stable when it gets reduced to +3 state
Why are MoO3 & WO3 not good oxidising agents?
They are already stable in +6 state so they don’t show a tendency to get reduced
Lowest state seen in 3d series
0 in the compound [Ni(CO)4]
Highest states are seen in
Oxide & flourides
Highest states are seen in oxide & flouride. Why?
Due to small sized electro -ve elements, so they are able to oxidise metal to higher state
Why is highest state of an element seen in oxide?
Due to ability of oxygen to form multiple bonds with the metal
Which magnetic moment is seen in transition elements?
spin
What decides spin MM & color?
unpaired e’s
Why are compds formed by Sc3+,Ag+ & Zn2+ colourless?
Since they don’t have unpaired e’s
Why are transition elements able to act as catalysts?
Since they can show different oxidation states
Why does Pt, Pd & Ni act as catalyst?
They have large surface area which provides area for the rn
Why are these elements able to form complexes?
Due to small size of ion, high charge of metal ion, availability of empty d orbitals
Interstitial compds?
Spaces in b/n atoms in metal lattice which are occupied by small atoms like C, N, H
interstitial compds are _________ compds
non-stoichiometric
Properties of interstitial compds
High MP, hard compds, retain their metallic conductivity, chemically inert
Alloys are
homogeneous substitutional solid soutions in which some of the metal atoms are replaced by other metals
Brass is made of
Cu & Zn
Bronze is made of
Cu & Tin
K2Cr2O7 is obtained from
Chromite ore when treated with Na2CO3 & O2 & heated
To convert chromate to dichromate,
acid is added
To convert dichromate to chromate,
base is added
color of (CrO4)2-
yellow
Color of (Cr2O7)2-
orange
Effect of H+ on CrO4?
It converts it to Cr2O7
Why does CrO4 show color despite having unpaired e’s?
Due to charge transfer
How is KMnO4 obtained?
K2MnO4 when kept for some time or when treated with acid give KMnO4
Colour of (MnO4)2-
green
Why does H undergo reduction instead of K+ in KMnO4 formation?
Since K+ has -ve potential since it is a metal
One property of Kr2CrO7?
It is a good oxidising agent in all mediums
Why is silver a transition element?
d orbitals are completely filled in d^10s^2
Why is enthalpy of atomisation lowest for Zn in 3d series?
d orbitals are not involved in bonding, so metallic bond is weak and energy to break them to atoms is low
how +2 state becomes more stable in 1st half of 3d series with increasing atomic number?
the 3d orbitals get gradually occupied and empty orbitals decrease so stability increases from Sc2+ to Mn2+
characteristics of d block elements?
- (n-1)d^1-10 ns^1-2
metallic lustre, high tensile strength, ductile, malleable - decrease in radius with increasing at. no
- Increasing ionisation enthalpy from left to right
- Increase in sum of 1st & 2nd ionisation enthalpies
- They form complexes
- They show dia & para magnetism
- Form coloured ions
- Used as catalysts
Transition elements have _______ electrical & thermal conductivity
high
Transition elements have ____ volatility
low
Transition elements have ______ MP
high
In what way is E.C of these elements different from non-transition elements?
In non-transition elements, d orbitals are absent or completely filled
Most common states by lanthanoids
2, 3 and 4
Why transition metals have high enthalpies of atomisation?
Due to large no of unpaired e’s. These atoms have strong interatomic interaction & stronger bonding
Why do these elements form coloured compds?
Due to partial absorption of visible light. The e’ absorbs the radiation of a particular freq & jumps to next orbital
How states differ in transition and non transition metals?
In non transition metals ,variation is selective ie they differ by 2 and states of transition elements differ by 1
Effect of increase in pH on K2Cr2O7
It changes to K2Cr2O4(orange to yellow)
Examples of disproportionation rns?
- 3MnO4 + 4H –> 2MnO4 + MnO2 + 2H2O
- 3CrO4 + 8H –> 2crO4 + Cr3+ + 4H2O
Example for lowest oxide is basic, highest oxide is acidic/amphoteric
MnO(Mn2+) ; Mn2O7(Mn7+)
Alloy which contains lanthanoid metals
mischmetal which has S, C, Ca & Al
Use of mischmetal
Produce bullets, shell & lighter flint
Elements of 1st series posess diff properties than those of heavier elements?
Due to larger atomic radii of heavier elements, high ionization and atomisation enthalpy, higher MP & BP
Ce exhibit
+4
Pr exhibit
+4
Tb exhibit
+4
Nd exhibit
+2
Sm & Eu exhibit
+2
Electronic COnfig for lanthanoids
[Xe]4f^1-14 5d^0-1 6s^2
Electronic Config for actinoids
[Rn]5f^1-14 6d^0-1 7s^2
Most stable state for lanthanoid
+3. Some show 2 & 4
Most stable state for actinoids
Besides three, 4,5,6, & 7 are seen
Reactivity of lanthanoids
Less reactive metals
Reactivity of actinoids
More reactive
Which doesn’t form oxocations?
Lanthanoids
Which forms complexed easily?
Actinoids
________ compds are less basic
lanthanoid
Which CuX2 will not be formed?
CuI2
As size of ion increases, its covalent nature
decreases
Why are Yb2+ & Eu2+ good reducing agents?
it will try to go to its stable +3 state and get oxidised
Why are Ce +4 & Tb 4+ good oxidising agents?
They show tendency to get reduced to +3 state to be stable
The only radioactive element in lanthanoids
Promethium(Pm)
Which has highest MP in lanthanoids?
Samarium(Sm) 1623K
Lanthanoids are good _______ agents
reducing
Lanthanoids have __ potential values
-ve
Most stable state in Lanthanoids
+3
Why is +2 state also shown by lanthanoids?
Stable half or filled orbitals
Atomic size _____ with increase in atomic no. due to poor shielding effect
decrease
Basic strength of hydroxides of lanthanoids
Decreases from Ce to Lu
Why does covalent nature increase when size of ion decrease?
When size is less, +ve ion will have greater polarising power to capture the e’ cloud of the anion due to which OH cannot be given easily(Fajan’s rules). So basicity decreases.
Does lanthanides show color & paramagnetism?
Yes
lanthanoids have spin &
orbital magnetic moment
Lanthanoid + H2O gives
LnOH3 + H2(displaces H)
uses of Lanthanoids
- Oxides are used as catalysts in cracking of petroleum
- Oxide used to make Crook’s lens for protection from UV rays
- Making Mischmetal
Pyrophoric alloy
Mischmetal + magnesium
Why is pyrophoric alloy used for making bullets?
It catches fire easily
Actinoid contraction
Poor shielding effect of 5f e’s
Why lanthanoids have greater ionisation energy than actinoids?
4f is near to nucleus than 5f so it can pull the e’s more than those of 5f
Why does actinides show more oxidation states?
Less diff in energy b/n 5f 6d 7s
Mn2O7 is acidic where MnO is basic
Mn has +7 in Mn2O7 which is more acidic
Acidic nature increase on _____ in oxidation states
Increasing
d block elements exhibit more oxidatoin states than f block
Less energy diff b/n d & s orbitals in d block
Zr & Hf have similar atomic radii
Lanthanoid contraction
Titration of FeSO4 with KMnO4 uses dil H2SO4 & not dil HCl. Why?
Chlorine produces greenish yellow gas which interrupts pale pink colour needed.
Co2+ is easily oxidised in presence of strong ligands
Co 2+ will easily lose 1 e’ to be stable
Transition elements have high enthalpy of atomisation. Why?
Due to strong metallic bonding due to unpaired e’s
