Chemistry 1 Marks Question

Th⁴⁺ = 1s², 2s², 2p⁶, 3s², 3p⁶, 3d¹⁰, 4s², 4p⁶, 4d¹⁰, 4f¹⁴, 5s², 5p⁶, 5d¹⁰, 6s², 6p⁶.

Lu²⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f ¹⁴ 5d¹
Or, [Xe]⁵⁴ 2f¹⁴ 3d³

Pm³⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f⁴
Or, [Xe]⁵⁴ 3d³

The extent of metallic bonding an element undergoes deideds the enthalpy of atomization the more extensive the metallic bonding of an element the more will be its enthalpy of atomization.
Sc & Zn belongs to 3^rd group of periodic table. In all transition metals (except Zn, electronic configuration: 3d¹⁰ 4s²), there are some unpaired electrons that account for their stronger metallic bonding. Due to the absence of these unpaired electrons, the inter-atomic electronic bonding is the weakest in Zn and as a result, it has the least enthalpy of atomization.

In the lanthanide series, +3 oxidation state is most common i.e., Ln(III) compounds are predominant. However, +2 and +4 oxidation states can also be found in the solution or in solid compounds.

Ce⁴⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶
Or, [Xe]⁵⁴

CO²⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁷
Or, [Ar]¹⁸d⁷

Mn (Z = 25) = 3d⁵4s²
Mn has the maximum number of unpaired electrons present in the d-subshell (5 electrons). Hence, Mn exhibits the largest number of oxidation states, ranging from +2 to +7.

The outer electronic configuration of Ag (Z = 47) is 4d¹⁰5s¹. It shows +1 and +2O.S. (in AgO and AgF₂). And in +2O.S. , the electronic configuration is d⁹ i.e., d - subshell is incompletely filled. Hence, it is a transition element.

Electronic configuration: The general electronic configuration of lanthanoids is [Xe]⁵⁴ 4f^1-14 5d^0·1 6s² and that of actinoids is [Rn]⁸⁶ 5f^0-14 6d^0-1 7s², lanthanoids belong to 4f series whereas actinoids belong to 5f-series.

Mn²⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵

Cr³⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d³
Or, [Ar]¹⁸ 3d³

Both oxide and fluoride ions are highly electronegative and have a very small size. Due to these properties, they are able to oxidize the metal to its highest oxidation state.

Cr²⁺ is a stronger reducing agent than Fe²⁺. This is because E°(Cr³⁺/Cr²⁺) is negative (-0.41 V) whereas E°(Fe³⁺/Fe²⁺) is positive (+ 0.77 V). Thus, Cr²⁺ is easily oxidised to Fe³⁺ but Fe²⁺ cannot be easily oxidised to Fe³⁺.

Lawrencium (Lr) is the last element in the series of antinoids.
Its electronic configuration is [Rn] 5f¹⁴ 6d¹ 7s². The possible oxidation state of Lawrencium is +3.

Cu⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰
Or, [Ar]¹⁸ 3d¹⁰

This is due to poor shielding by 5f-electrons in the actinoids than that by 4f e^-1s in lanthanoids.

All transition elements contain incompletely filled d-subshell whereas the outer shell electronic configuration remains the same.

Pyrophoric alloys emit sparks when struck. Hence, they are used in making flints for lighters.

CrO < Cr₂O₃ < CrO₃. Higher the oxidation state, more will be acidic character.

The regular decrease in the atomic and ionic radii/(having the same charge) of Lanthanoids with increasing atomic number is known as Lanthanoid contraction.

because of the completely filled 3d sub shell no unpaired electron is left for metallic bonding.

Stability of complexes from La to Lu, increases as the size of the central atom decreases.

The common oxidation state of Cu, Ag and Au is +1.

The last electron enters (n - 1) d-orbital, i.e., d-orbital of the penultimate shell. Hence, these are known as d-block elements.

40 elements.

The acidic nature of lanthanoid oxides increases from La to Lu.

5f^1-14 6d^0-1 7s².

Mn²⁺ has the maximum paramagnetic character because of the maximum number of unpaired electrons, viz., 5.

This is because Fe (3d⁶ 4s¹) has four unpaired electrons in 3d-subshell. While Cu (3d¹⁰ 4s¹) has only one electron in the 4s-subshell. Hence, metallic bonds in Fe are much stronger than those in Cu.

On the basis of electrochemical series, the standard electrode potential shows the following order:
E°Mn²⁺/Mn < E°Cr²⁺/Cr < E°Fe²⁺/Fe < E°CO²⁺/CO
Therefore, Co²⁺ gets easily reduced to metallic cobalt while it is difficult to reduce Mn²⁺. Hence, Mn²⁺ will be the most stable and the increasing stability order will be
Co²⁺ < Fe²⁺ < Cr²⁺ < Mn²⁺

MnO₄^- / KMnO₄

Due to lanthanoid contraction, they have almost same size (Zr = 160 pm) and (Hf = 159 pm).

+3 is the most common oxidation state of lanthanoids.

Potassium permanganate (KMnO₄) in which manganese shows +7 oxidation state.

Cerium exhibits both +3 and +4 oxidation states.

Lanthanoids are called f-block elements because the last electron in them enters into f-orbital.

As the size decreases from La to Lu, stability of oxosalts also decreases.

Zr and Hf have similar ionic size.

This is due to the increasing stability of the lower species to which they are reduced.

Exchange the second ionization enthalpy shows unusually high values for Cr and Cu first transition series where the d⁵ and d¹⁰ configuration of the M⁺ ions are disrupted, with considerable loss of energy.

This is due to comparable energies of 5f, 6d and 7s orbitals.