Actinoid contraction is greater from element to element than lanthanoid contraction. Why?
This is due to poor shielding by 5f-electrons in the actinoids than that by 4f e-1s in lanthanoids.
Assertion (A): Cu can not libirate hydrogen from acids .
Reason (R): because it has positive electrode potential.
Actinoid contraction is greater from element to element than lanthanoid contraction. Why?
In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct answer out of the following choices:
(a) Both Assertion and Reason are true and the Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are true and the Reason is not the correct explanation of Assertion.
(c) Assertion is not true but the Reason is true.
(d) Both Assertion and Reason are false.
Assertion (A): Cu2+ iodide is not known.
Reason (R): Cu2+ oxidises I to iodine.
Assertion (A): The highest oxidation state of osmium is +8.
Reason (R): Osmium is a 5d-block element.
Calculate the number of unpaired electrons in the following gaseous ions : Mn3+, Cr3+, V3+ and Ti3+. Which one of these is the most stable in aqueous solution.
What may be the stable oxidation state of the transition element with the following delectron configurations in the ground state of their atoms: 3d3,3d5, 3d8 and 3d4?
While filling up of electrons in the atomic orbitals, the 4s orbital is filled before the 3d-orbital but reverse happens during the ionization of the atom. Explain why?
When a chromite ore (A) is fused with sodium carbonate in free excess of air and the product is dissolved in water, a yellow solution of compound (B) is obtained. After treatment of this yellow solution with sulphuric acid, compound (C) can be crystallized from the solution. When compound (C) is treated with KCl, orange crystals of compound (D) crystallise out. Identify A to D and also explain the reactions.
In the form of dichromate, Cr (VI) is a strong oxidizing agent in acidic medium but Mo (VI) in MoO3 and W (VI) in WO3 are not because
(a) Cr (VI) is more stable than Mo(VI) and W(VI)
(b) Mo(VI) and W(VI) are more stable than Cr(VI)
(c) higher oxidation states of heavier members of group-6 of transition series are more stable
(d) lower oxidation states of heavier members of group-6 of transition series are more stable
Although Zr belongs to 4d and Hf belongs to 5d transition series but it is quite difficult to separate them. Why?
Although fluorine is more electronegative than oxygen, but the ability of oxygen to stabilize higher oxidation states exceeds that of fluorine. Why?
How would you account for the irregular variation of ionisation enthalpies (first and second) in the first series of the transition elements?
Silver atom has completely filled d orbitals (4d10) in its ground state. How can you say that it is a transition element?
Name the oxometal anions of the first series of the transition metals in which the metal exhibits the oxidation state equal to its group number.
Explain giving reasons:
(i)Transition metals and many of their compounds show paramagnetic behaviour.
(ii)The enthalpies of atomisation of the transition metals are high.
(iii)The transition metals generally form coloured compounds.
(iv)Transition metals and their many compounds act as good catalyst
While filling up of electrons in the atomic orbitals, the 4s orbital is filled before the 3d-orbital but reverse happens during the ionization of the atom. Explain why?
Assertion (A): The highest oxidation state of osmium is +8.
Reason (R): Osmium is a 5d-block element.
Describe the preparation of potassium dichromate from iron chromite ore. What is the effect of increasing pH on a solution of potassium dichromate?
Calculate the number of unpaired electrons in the following gaseous ions : Mn3+, Cr3+, V3+ and Ti3+. Which one of these is the most stable in aqueous solution.
In what way is the electronic configuration of the transition elements different from that of the non transition elements?
What are interstitial compounds? Why are such compounds well known for transition metals?
Compare the stability of +2 oxidation state for the elements of the first transition series.
Metallic radii of some transition elements are given below. Which of these elements will have highest density?
Generally, transition-elements and their salts are coloured due to the presence of unpaired electrons in metal ions. Which of the following compounds are coloured?
(a) kMnO4 (b) Ce(SO4)2 (c) TiCl4 (d) Cu2Cl2
Which of the following lanthanoids show +2 oxidation state besides the characteristic oxidation state +3 of lanthanoids?
(a) Ce (b) Eu (c) Yb (d) Ho
Although +3 is the characteristic oxidation state for lanthanoids but cerium
also shows +4 oxidation state because
(a) it has variable ionization enthalpy
(b) it has a tendency to attain noble gas configuration
(c) it has a tendency to attain f ° configuration
(d) it resembles Pb4+
In the series Sc (Z = 21) to Zn (Z = 30), the enthalpy of atomisation of zinc is the lowest, i.e., 126 kJ mol-1 . Why?
Describe the oxidising action of potassium dichromate and write the ionic equations for its reaction with:
(i) iodide
(ii) iron (II) solution and
(iii) H2S
Predict which of the following will be coloured in aqueous solution? Ti3+, V3+,Cu+, Sc3+, Mn2+, Fe3+ and Co2+ Give reasons for each.
How would you account for the following:
(i) Of the d4 species, Cr2+ is strongly reducing while manganese (III) is strongly oxidizing.
(ii) Cobalt (II) is stable in aqueous solution but in the presence of complexing reagents it is easily oxidised.
(iii) The d1 configuration is very unstable in ions.
What is meant by disproportionation? Give two examples of disproportionation reaction in aqueous solution.
Which metal in the first series of transition metals exhibits + 1 oxidation state most frequently and why?
Indicate the steps in the preparation of:
(i) K2Cr207from chromite ore
(ii) KMn04 from pyrolusite ore.
Which is the last element in the series of the actinoids? Write the electronic configuration of this element. Comment on the possible oxidation state of this element
When KMnO4 solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because
(a) CO2 is formed as the product (b) Reaction is exothermic
(c) Mn04 catalyses the reaction (d) Mn2+ acts as autocatalyst
KMnO4 acts as an oxidizing agent in acidic medium. The number of moles of KMn04 that will be needed to react with one mole of sulphide ions in acidic solution is
Gadolinium belongs to 4f series. Its atomic number is 64. Which of the following is the correct electronic configuration of gadolinium?
Which of the following actinoids show oxidation states up to +7?
(a) Am (b) Pu (c) U (d) Np
Transition elements form binary compounds with halogens. Which of the following elements will form MF3 type compounds?
(a) Cr (b) Co (c) Cu (d) Ni
When a brown compound of manganese
(A) is treated with HCl, it gives a gas
(B) The gas taken in excess, reacts with NH3 to give an explosive compound
(C) Identify compounds A, B and C.
Mention the type of compounds formed when small atoms like H, C and N get trapped inside the crystal lattice of transition metals. Also give physical and chemical characteristics of these compounds.
