Write down the electronic configuration of (i) Cr3+ (ii) Pm3+ (iii) Cu+ (iv) Ce4+(v) Co2+ (vi) Lu2+(vii) Mn2+ (viii) Th4+.
(i) Cr3+ = [Ar]183d3
(ii)Pm3+ = [Xe]54 4f4
(iii)Cu+ = [Ar]18 3d10
(iv)Ce4+ = [Xe]54
(v)Co2+ = [Ar]18 3d7
(vi)Lu2+ = [Xe]54 4f14 5d1
(vii) Mn2+ = [Ar]18 3d5 (viii)Th4+= [Rn]86
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?
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.
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?
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.
Indicate the steps in the preparation of:
(i) K2Cr207from chromite ore
(ii) KMn04 from pyrolusite ore.
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.
Comment on the statement that elements of the first transition series possess many properties different from those of heavier transition elements.
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
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?
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.
Describe the preparation of potassium dichromate from iron chromite ore. What is the effect of increasing pH on a solution of potassium dichromate?
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.
Which of the following ions show higher spin only magnetic moment value?
(a) Ti3+ (b) Mn2+ (c) Fe2+ (d) Co3+
(a) Transition metals can act as catalysts because these can change their oxidation state.
How does Fe(III) catalyse the reaction between iodide and persulphate ions?
(b) Mention any three processes where transition metals act as catalysts.
Write down the electronic configuration of (i) Cr3+ (ii) Pm3+ (iii) Cu+ (iv) Ce4+(v) Co2+ (vi) Lu2+(vii) Mn2+ (viii) Th4+.
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
What are the characteristics of the transition . elements and why are they called transition elements? Which of the d-block elements may not be regarded as the transition elements?
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
What are inner transition elements? Decide which of the following atomic numbers are the atomic numbers of the inner transition elements: 29,59,74,95,102,104.
Name the members of the lanthanoid series which exhibit+4oxidatk>nstatesandthosewhichexhibit +2 oxidation states. Try to correlate this type of behaviour with the electronic configurations of these elements.
Metallic radii of some transition elements are given below. Which of these elements will have highest density?
Silver atom has completely filled d orbitals (4d10) in its ground state. How can you say that it is a transition element?
How would you account for the irregular variation of ionisation enthalpies (first and second) in the first series of the transition elements?
Predict which of the following will be coloured in aqueous solution? Ti3+, V3+,Cu+, Sc3+, Mn2+, Fe3+ and Co2+ Give reasons for each.
Compare the chemistry of actinoids with that of the lanthanoids with special reference to
(i) electronic configuration,
(ii) atomic and ionic sizes and
(iii) oxidation state
(iv) chemical reactivity.
Gadolinium belongs to 4f series. Its atomic number is 64. Which of the following is the correct electronic configuration of gadolinium?
Assertion (A): Separation of Zr and Hf is difficult.
Reason (R): Because Zr and Hf lie in the same group of the periodic table.
What are interstitial compounds? Why are such compounds well known for transition metals?
Predict which of the following will be coloured in aqueous solution? Ti3+, V3+,Cu+, Sc3+, Mn2+, Fe3+ and Co2+ Give reasons for each.
The chemistry of the actinoid elements is not so smooth as that of the lanthanoids. Justify this statement by giving some examples from the oxidation state of these elements.
Transition elements show magnetic moment due to spin and orbital motion of electrons. Which of the following metallic ions have almost same spin only magnetic moment?
(a) Co2+ (b) Cr2+ (c) Mn2+ (d) Cr3+
Which of the following actinoids show oxidation states up to +7?
(a) Am (b) Pu (c) U (d) Np
General electronic configuration of actinoids is (n – 2)f1-14 (n – 1 )d0-2 ns2. Which of the following actinoids have one electron in 6d orbital?
(a) U (Atomic no. 92) (b) Np (Atomic no. 93)
(c) Pu (Atomic no. 94) (d) Am (Atomic no. 95)
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
Which of the following will not act as oxidizing agents?
(a) CrO3 (b) MoO3(c) WO3 (d) CrO42-
