Explore topic-wise InterviewSolutions in Current Affairs.

(a) Both (A) and (R) are correct and (R) explains (A).

1. Zn, Cd, Hg belong to d-block elements even though they do not have partially filled d-orbitals either in their elemental state or in their normal oxidation states.

2. However they are treated as transition elements, because their properties are an extension of the properties of the respective transition elements.

1. All the transition elements are metals. They are good conductors of heat and electricity. Of all the known elements, silver has the highest electrical conductivity at room temperature. 

2. Most of the transition elements are hexagonal close packed, cubic close packed or body centered cubic which are the characteristics of true metals.

(b) [Ar] 3d’ 4s²

(a) Both (A) and (R) are correct and (R) explains (A).

1. As we move from left to right along the transition metal series, melting point first increases as the number of unpaired d electrons available for metallic bonding increases, reach a maximum value and then decreases, as the d electron pairs up and become less available for bonding.

2. For example, in the first series the melting point increases from Scandium to a maximum of 2183 K for Vanadium, which is close to 2180K for chromium. 

3. Manganese in 3d series and has low melting point. The maximum melting point at about the middle of transition metal series indicates that d⁵ configuration is favorable for strong interatomic attraction.

(b) Hf, Zr

This pair has same atomic radius whereas others have different atomic radius.

There are 4 series in d-block elements 

They are, 

3d series – 4th period – Scandium to Zinc 

4d series – 5th period – Yttrium to Cadmium 

5d series – 6th period – Lanthanum to Mercury 

6d series – 7th period – Actinium to Californium

(a) Both (A) and (R) are correct and (R) explains (A).

(b) (i), (ii) and (iii)

1. As we move from Ce³⁺ to Lu³⁺ , the basic character of Lu³⁺ ions decreases. 

2. Due to the decrease in the size of Lu³⁺ ions, the ionic character of Lu – OH bond decreases, covalent character increases which results in the decrease in the basicity. 

3. Hence, La(OH)₃ is more basic than Lu(OH)₃.

(a) La(OH)₂ is less basic than Lu(OH)₃

Cr₂O₃ is amphoteric in nature.

Cu²⁺ is paramagnetic in nature.

(a) Both (A) and (R) are correct and (R) is the correct explanation

(c) Vitamin-B₁₂

(b) (iii) only

Cu⁺ , Zn²⁺ electronic configuration [Ar] 3d¹⁰

The number of unpaired electron is 0.

µ = \(\sqrt{0(0+2)}\) = 0 µ_B. Cu⁺ , Zn²⁺ are diamagnetic. 

1. All the transition metals are hard. 

2. Most of them are hexagonal close packed, cubic close packed (or) body centered cubic which are characteristics of true metals. 

3. The maximum melting point at about the middle of transition metal series indicates that d⁵ configuration of favourable for strong inter atomic attraction. 

4. Due to the strong metallic bonds, atoms of the transition elements are closely packed and held together. This leads to high melting point and boiling point.

1. Transition metal is an element whose atom has an incomplete d sub shell or which can give rise to cations with an incomplete d sub shell.

2. They occupy the central position of the periodic table, between s-block and p-block elements. 

3. Their properties are transitional between highly reactive metals of s-block and elements of pblock which are mostly non metals. 

4. Example – Iron, Copper, Tungsten, Titanium.

(a) (ii) and (iv)

1. d-block elements occupy the central position of the periodic table, between s and p block elements. 

2. Their properties are transitional between highly reactive metals of s-block and elements of p-block which are mostly non-metals. That is why d-block elements are called transitional elements.

(c) TiCl₄ + Al(C₂H₅)₃

1. In sixth period after lanthanum, the electrons are preferentially filled in inner 4f sub shell and these 14 elements following lanthanum show similar chemical properties. Therefore these elements are grouped together and placed at the bottom of the periodic table. This position can be justified as follows.

• Lanthanoids have general electronic configuration [Xe] 4f^2-14 5d^0-1 6s² 
• The common oxidation state of lanthanoids is +3
• All these elements have similar physical and chemical properties.

2. Similarly the fourteen elements following actinium resemble in their physical and chemical properties.

3. If we place these elements after Lanthanum in the periodic table below 4d series and actinides below 5d series, the properties of the elements belongs to a group would be different and it would affect the proper structure of the periodic table.

4. Hence a separate position is provided to the inner transition elements at the bottom of the periodic table.

1. Many industrial processes use transition metals or their compounds as catalysts. Transition metal has energetically available d orbitals that can accept electrons from reactant molecule or metal can form bond with reactant molecule using its ‘d’ electrons.

2. For example, in the catalytic hydrogenation of an alkene, the alkene bonds to an active site by using its n electrons with an empty d orbital of the catalyst.

La(OH)₃ is more basic in nature.

Extraction of iron is carried out in Blast furnace.

Composition of Haematite ore is Fe₂O₃ + SiO₂ + Al₂O₃ + phosphates

1. sandpblock 

2. group-II 

3. cobalt 

4. Titanium 

5. symmetrical distribution 

6. silver 

7. d⁵ , inter atomic 

8. lanthanoid contraction 

9. more stable 

10. Scandium

1. Rh/Ir complex 

2. CO₂(CO)₈ 

3. Zeigler – Natta (or) TiCl₄ + Al(C₂H₅)₃

4. inert

5. ionic 

6. amphoteric, basic

7. permanganic acid (HMnO₄)

8. Chromium (III) oxide – Cr₂O₃

9. Potassium dichrom.ate

10. iron compounds, iodides

Haematite ore is reduced using coke and CO. Carbon in the coke is converted to carbon monoxide. Carbon and carbon monoxide together reduce Fe₂O₃ to metallic iron.

Fe₂O₃ + 3C → 2Fe + 3CO. 

Fe₂O₃ + 3CO → 2Fe + 3CO₂.

1. Manganese 

2. + 8

3. Copper

4. reducing, oxidising

5. Standard electrode potential

6. powerful reducing agent

7. diamagnetism

8. μ = g\(\sqrt {S(S+1)}\) μ_B

9. transition metals, compounds

10. Nickel

(a) Manganese

Neptunium and Plutonium exhibit the maximum oxidation state as +7

• The most stable oxidation state of lanthanoids is + 3.
• Hence, Eu²⁺ and Yb²⁺ tend to get + 3 oxidation states by losing one electron.
• Since they get oxidised, they are good reducing agents in + 2 oxidation state.

(d)  (iii) only

• Manganese (₂₅Mn) has electronic configuration. ₂₅Mn [Ar]¹⁸3d⁵4s².
• Mn has stable half-filled d-subshell.
• Due to a small difference in energy between 3d and 4s-orbitals, Mn can lose or share electrons from both the orbitals, hence shows variable oxidation states.
• Mn shows oxidation states ranging from + 2 to + 7. 

Stable oxidation states : 

Plutonium + 3 to + 7 

Cerium + 3, + 4 

Manganese + 2, + 4, + 6, + 7 

Europium +2, + 3

1. The first transition metal Scandium exhibits only +3 oxidation state, but all other transition elements exhibit variable oxidation states by loosing electrons from (n-l)d orbital and ns orbital as the energy difference between them is very small.

2. At the beginning of the 3d series, +3 oxidation state is stable but towards the end +2 oxidation state becomes stable. 

3. The number of oxidation states increases with the number of electrons available, and it decreases as the number of paired electrons increases. For example, in the 3d series, first element Sc has only one oxidation state +3 the middle element Mn has six different oxidation states from +2 to +7. The last element Cu shows +1 and +2 oxidation states only.

 4. Mn²⁺ (3d⁵) is more stable than Mn⁴⁺ (3d³) is due to half filled stable configuration.

1. Copper has a positive reduction potential. Elemental copper is more stable than Cu²⁺ . 

2. Copper having positive sign for electrode potential merely means that copper can undergo reduction at faster rate than reduction of hydrogen. 

3. The electron giving reaction (oxidation) of copper is slower than that of hydrogen. It is determined from the result of S.H.E (Standard Hydrogen Electrode) potential value experiment.

Oxidation state of Manganese in

(i) \(MnO^{2-}_4\) is + 6

(ii) \(MnO^-_4\) is +7

Steps in the manufacture of potassium dichromate from chromite ore are :

Concentration of chromite ore.

Conversion of chromite ore into sodium chromate (Na₂CrO₄).

Conversion of Na₂CrO₄ into sodium dichromate (Na₂Cr₂O₇).

Conversion of Na₂Cr₂O₇ into K₂Cr₂O₇.

(i) Sc³⁺ salts are colourless :

• The electronic configuration of ₂₁Sc [Ar| 3d¹4s² and Sc³⁺ [Ar] d°.
• Since there are no unpaired electrons in 3d subshell, d → d transition is not possible.
• Therefore, Sc³⁺ ions do not absorb the radiations in the visible region. Hence salts of Sc³⁺ are colourless (or white).

(ii) Ti⁴⁺ salts are colourless :

• The electronic configuration of ₂₂Ti [Ar] 3d²4s² and Ti⁴⁺ : [Ar] d°
• Since there are no unpaired electrons in 3d subshell, d-*d transition is not possible.
• Therefore, Ti³⁺ ions do not absorb the radiation in visible region. Hence salts of Ti³⁺ are colourless.

 (iii) Vs⁵⁺ salts are eolourless :

• The electronic configuration of ₂₃V : [Ar] 3d²4s² and V⁵⁺ : [Ar] 3d° 
• Since there are no unpaired electrons in 3d-subshell, d – d transition is not possible. 
• Therefore, V⁵⁺ ions do not absorb the radiations in the visible region. Hence, V⁵⁺ salts are colourless, a

(b) Ti³⁺ , Ti²⁺

Have d¹ and d¹ configuration whereas others have same configuration.

1. Sc³⁺ , Ti⁴⁺, V⁵⁺ have d° electronic configuration, n = 0

2. µ = \(\sqrt{0(0+2)}\) = 0 µ_B So they are diamagnetic

(d) Cu²⁺

Reason: It is paramagnetic whereas others are diamagnetic

• V³⁺[Ar]¹⁸ 3d² -(green) Since there are two unpaired electrons available, for d → d transition, it will show a Green colour.
• Sc³⁺[Ar]¹⁸3d° (colourless/white). Since there are no unpaired electrons in the 3d subshell, it will not show colour.
• Cr³⁺[Ar]¹⁸ 3d³ – (violet) There are three unpaired electrons in the 3d subshell, hence due to d → d transition, it will show violet colour.
• Cu²⁺[Ar]¹⁸ 3d⁹(blue) It has one unpaired electron that can undergo a d → d transition, hence it will show the colour blue
• Ti³⁺ [Ar]¹⁸ 3d¹ (purple) It has one unpaired electron that can undergo a d → d transition, hence it will show the colour purple.
• Cu¹⁺ [Ar]¹⁸ 3d¹⁰(colourless) There are no unpaired electrons in the 3d subshell, hence it will not show colour. 

When it passes through centre of curvature.

If light rays appear as if they are coming from a point after reflection, then we say light rays are diverging.

Aim :

To show diverging and converging of light by using laser lights. 

Material required : 

Concave mirror, convex mirror, laser lights-2, screen, V-stand, Agarbathi. 

Procedure:

• Place a concave mirror on a V-stand and place the V-stand on a table. 
• Take two laser lights. 
• Focus the light rays of laser lights parallel to the axis of the concave mirror.
• The light rays (beams) incident on the concave mirror are reflected back and converge at one point. 
• Place the screen to catch that converging point of reflected light rays. 
• Light a Agarbathi near the table.

Observation : 

We can observe path of the incident and reflected rays clearly in the smoke of Agarbathi. 

• Now place a convex mirror on the stand. 
• Again pass the laser light rays parallel to the principal axis at the convex mirror. 

Observation : 

We can observe diverging light rays. We cannot catch any converging point on the screen.