Observe the table given below belonging to 3d series, their first, second, third ionisation enthalpy and \(\mathbf{E}_{\mathbf{M}^{2+} / \mathbf{M}}^{\circ}\) and \(\mathbf{E}_{\mathbf{M}^{3+} / \mathbf{M}^{2+}}^{\circ}\) and answer the questions that follow based on table and related concepts.

(a) Why does zinc have highest first ionisation enthalpy?
(b) Why is 3 rd ionisation enthalpy of Mn high?
(c) Why is Cr^{3 +} more stable than Cr²⁺?
(d) Why is \(\mathbf{E}_{\mathbf{M n}^{2+} / \mathbf{M n}}^{\circ}-\mathbf{1 . 1 8 V} ?\)
(e) Why is \(\mathbf{E}_{\mathbf{C n}^{2+} / \mathrm{Cn}}^{\circ}+\mathbf{0 . 3 4 V} ?\)
(f) Why is Fe³⁺ more stable than Fe²⁺?
(g) Why is Mn ^{3 +} good oxidising agent and \(\mathbf{E}_{\mathbf{M n}^{3+} / \mathrm{Mn}^{2+}}^{\circ}=\mathbf{1 . 5 7 V} ?\) 

Observe the graph of transition metal and their melting points and answer the questions based on the graph and related concepts.

(a) Why does W (tungsten) has highest melting point?
(b) Which element in 3d series has lowest enthalpy of atomisation and why?
(c) Why is mercury liquid?
(d) Why are transition metals less electropositive than 's'-block elements?
(e) How does density vary from left to right in 3d series and why?

The d-block of the periodic table contains the elements of the groups 3 to 12 and are known as transition elements. In general, the electronic configuration of these elements is \((n-1) d^{1-10} n s^{1-2}\). The d-orbitals of the penultimate energy level in their atoms receive electrons giving rise to the three rows of the transition metals i.e. 3d, 4d and 5d series. However Zn, Cd and Hg are not regarded as transition elements. Transition elements exhibit certain characteristic properties like variable oxidation stables, complex formation, formation of coloured ions, alloys, catalytic activity etc. Transition metals are hard (except Zn, Cd and Hg) and have a high melting point. 
(a) Why are Zn, Cd and Hg non-transition elements?
(b) Which transition metal of 3d series does not show variable oxidation state?
(c) Why do transition metals and their compounds show catalytic activity?
(d) Why are melting points of transition metals high?
(e) Why is Cu²⁺ ion coloured while Zn²⁺ ion is colourless in aqueous solution?

KMnO₄ and K₂Cr ₂O₇ are most important chemicals which are used as oxidising agents and disinfectants. K2MnO4 is prepared by fusing MnO₂ with KOH in presence of O₂.K₂MnO ₄ is electrolysed to get purple coloured KMnO₄ . Na₂CO₄ is prepared by heating chromite ore with Na₂CO₃ in presence of O₂. Na₂CrO₄ is converted into Na₂Cr₂ O₇ by reacting with concentrated H₂ SO₄ , Na₂Cr₂ O₇ is reacted with KCI to get K₂Cr₂O₇ orange coloured solid, soluble in water, changes to yellow coloured \(\mathrm{CrO}_{4}^{2-}\) in basic medium, KMnO₄ acts as oxidising agent in acidic, neutral as well tasic medium. In acidic medium, it converts Fe²⁺ to Fe^{3 +}, Sn²⁺ to Sn⁴⁺,  to CO₂. In asic medium it converts I^- to \(\mathrm{IO}_{3}^{-} \cdot \mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\) acts as oxidising agent only in acidic medium, converts H₂S to S, SO₂ to \(\mathrm{SO}_{4}^{2-}, \mathbf{I}^{-}\) to I₂. Lanthanoids and actinoids belong to f-block elements with general electronic configuration \((n-2) f^{1 \text { to } 14}(n-1) d^{0-2} n s^{2}\) . All actinoids are radio active. Both show contraction in atomic and ionic radii but actinoid contraction is more than lanthanoid contraction. Lanthanoid show +3 oxidation state, few elements show +2 and +4 oxidation states also. Actinoids show +3, +4, +5, +6, +7 oxidation states.
(a) Which lanthanoid shows +4 oxidation state and why?
(b) Give two similarity between lanthanoids and actinoids.
(c) Complete the equation and balance:
\(\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}+\mathrm{Fe}^{2+}+\mathrm{H}^{+} \longrightarrow\)
(d) Convert sodium chromate to sodium dichromate. Give chemical equation.
(e) Complete the following:
\(\mathbf{3} \mathbf{M n} \mathbf{O}_{4}^{2-}+\mathbf{4} \mathbf{H}^{+} \longrightarrow\)

Read the passage given below and answer the following questions:
Transition elements are elements that have partially filled d-orbitals. The configuration of these elements corresponds to (n - 1)d^1-10 ns^1-2. It is important to note that the elements mercury, cadmium and zinc (Ire not considered transition elements because of their electronic configurations, which corresponds to (n - 1)d^1-10 ns².
Some general properties of transition elements are :
These elements can form coloured compounds and ions due to d-d transition;
These elements exhibit many oxidation states;
A large variety of ligands can bind themselves to these elements, due to this, a wide variety of stable complexes formed by these ions. The boiling and melting point of these elements are high. These elements have a large ratio of charge to the radius.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: Tungsten has very high melting point.
 Reason: Tungsten is a covalent compound.
(ii) Assertion: Zn, Cd and Hg are normally not considered transition metals.
Reason: d-Orbitals in Zn, Cd and Hg elements are completely filled, hence these metals do not show the general characteristics properties of the transition elements.
(iii) Assertion: Copper metal gets readily corroded in acidic aqueous solution such as HCI and dil. H₂SO₄
Reason: Free energy change for this process is positive.
(iv) Assertion: Tailing of mercury occurs on passing ozone through it.
Reason: Due to oxidation of mercury.

Read the passage given below and answer the following questions:
Transition metal oxides are compounds formed by the reaction of metals with oxygen at high temperature. The highest oxidation number in the oxides coincides with the group number. In vanadium, there is a gradual change from the basic V₂O₃ to less basic V₂O₄ and to amphoteric V₂O_5・V₂O₄ dissolves in acids to give VO²⁺ salts. Transition metal oxides are commonly utilized for their catalytic activity and semiconductive properties. Transition metal oxides are also frequently used as pigments in paints and plastic. Most notably titatnium dioxide. One of the earliest application of transition metal oxides to chemical industry involved the use of vanadium oxide for catalytic oxidation of sulfur dioxide to sulphuric acid. Since then, many other applications have emerged, which include benzene oxidation to maleic anhydride on vandium oxides; cyclohexane oxidation to adipic acid on cobalt oxides. An important property of the catalyst material used in these processes is the ability of transition metals to change their oxidation state under a given chemical potential of reductants and oxidants.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Which oxide of vanadium is most likely to be basic and ionic ?

(ii) Vanadyl ion is

(iii) The oxidation state of vanadium in V₂O₅ is

(iv) Identify the oxidising agent in the following reaction.

Read the passage given below and answer the following questions:
The unique behaviour of Cu, having a positive E^o accounts for its inability to liberate H₂ from acids. Only oxidising acids (nitric and hot concentrated sulphuric acid) react with Cu, the acids being reduced. The stability of the half-filled (d⁵) subshell in Mn²⁺ and the completely filled (d¹⁰ ) configuration in Zn²⁺ are related to their E^o (M³⁺ /M²⁺) values. The low value for Sc reflects the stability of Sc³⁺ which has a noble gas configuration. The comparatively high value for Mn shows that Mn²⁺(d⁵) is particularly stable, whereas a comparatively low value for Fe shows the extra stability of Fe³⁺ (d⁵). The comparatively low value for V is related to the stability of V²⁺ (half-filled t_2g level).
The following questions are multiple choice questions.Choose the most appropriate answer :
(i) Standard reduction electrode potential of Zn²⁺ /Zn is - 0.76 V. This means

(ii) E^o values for the couples Cr³⁺/Cr²⁺ and Mn³⁺ /Mn²⁺ are -0.41 and +1.51 volts respectively. These values suggest that

(iii) The reduction potential values of M, Nand O are +2.46, -1.13 and -3.13 Y respectively. Which of the following order is correct regarding their reducing property?

(iv) Which of the following statements are true?
(i) Mn²⁺ compounds are more stable than Fe²⁺ towards oxidation to +3 state.
(ii) Titanium and copper both in the first series of transition metals exhibits +1 oxidation state most frequently.
(iii) Cu⁺ ion is stable in aqueous solutions.
(iv) The E⁰ value for the Mn³⁺ /Mn²⁺ couple is much more positive than that for Cr³⁺/Cr²⁺ or Fe³⁺/Fe²⁺.

Read the passage given below and answer the following questions:
The transition elements have incompletely filled d-subshells in their ground state or in any of their oxidation states. The transition elements occupy position in between s- and p-blocks in groups 3-12 of the Periodic table. Starting from fourth period, transition elements consists of four complete series : Sc to Zn, Y to Cd and La, Hf to Hg and Ac, Rf to Cn. In general, the electronic configuration of outer orbitals of these elements is (n - 1) d^1-10 ns^1-2. The electronic configurations of outer orbitals of Zn, Cd, Hg and Cn are represented by the general formula (n - 1)d¹⁰ n². All the transition elements have typical metallic properties such as high tensile strength, ductility, malleability. Except mercury, which is liquid at room temperature, other transition elements have typical metallic structures. The transition metals and their compounds also exhibit catalytic property and paramagnetic behaviour. Transition metal also forms alloys. An alloy is a blend of metals prepared by mixing the components. Alloys may be homogeneous solid solutions in which the atoms of one metal are distributed randomly among the atoms of the other.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) Which of the following characteristics of transition metals is associated with higher catalytic activity?

(ii) Transition elements form alloys easily because they have

(iii) The electronic configuration of tantalum (Ta) is

(iv) Which one of the following outer orbital configurations may exhibit the largest number of oxidation states?

Read the passage given below and answer the following questions:
The f-block elements are those in which the differentiating electron enters the (n -2) forbital. There are two series of f-block elements corresponding to filling of 4f and 5f-orbitals. The series of 4f- orbitals is called lanthanides. Lanthanides show different oxidation states depending upon stability of f⁰, f⁷ and f¹⁴ configurations, though the most common oxidation states is +3. There is a regular decrease in size of lanthanides ions with increase in atomic number which is known as lanthanide contraction.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The atomic numbers of three lanthanide elements X, Y and 2 are 65, 68 and 70 respectively, their Ln³⁺ electronic configuration is

(ii) Lanthanide contraction is observed in

(iii) Name a member of the lanthanoid series which is well known to exhibit +4 oxidation state.

(iv) Identify the incorrect statement among the following.