Yb²⁺ - 4f¹⁴ - no unpaired electrons - diamagnetic

+7       +2+3          2+              3+       4+
MnO₄^- + FeC₂O₄ ⟶ Mn²⁺ + Fe³⁺ + 2CO₂
5e^- acception       3e^- release
5 moles of FeC₂O₄ \(\equiv\) 3 moles of KMnO₄
1 mole of FeC₂O₄ \(\equiv\) (3/5) moles of KMnO₄
1 mole of FeC₂O₄ \(\equiv\) 0.6 moles of KMnO₄

MnO^-₄ + 8H⁺ + 5e^- → Mn²⁺ + 4H₂O

Cr²⁺ is stronger reducing agent than Fe²⁺. The standard electrode potential (E⁰) of Cr²⁺ is -0.91 V and that of Fe²⁺ is only -0.44 V.
If the standard electrode potential of a metal is large and negative is a powerful reducing agent, because it loses electrons easily.
Hence Cr²⁺ is stronger reducing agent.

(i) In the actinoid series, the elements have poor shielding effect when compared with lanthanide series.
(ii) Hence in the actinoid series, when atomic number increases the effective nuclear charge also increases so actinoid contraction is greater from element to element than the lanthanoid contraction.

S.No	Lanthanoids	Actinoids
1.	Differentiating electron enters in 4f orbital	Differentiating electron enters in 5f orbital
2.	Binding energy of 4f orbitals are higher	Binding energy of 5f orbitals are lower
3.	They show less tendency to form complexes	They show greater tendency to form complexes
4.	Most of the lanthanoids are colourless	Most of the actinoids are coloured For Example: U3+ (red) U4+ (green).
5.	They do not form oxo cations	They do form oxo cations such as UO22+, NpO22++ etc.
6.	Besides +3 oxidation states lanthanoids show +2 and +4 oxidation states in few cases	Besides +3 oxidation states actinoids show higher oxidation states such as +4, +5, +6 and +7

(i) The elements in which the extra electron enters (n-2) f orbitals are called f-block elements. These elements are called as inner transition elements because they form a transition. Series within the transition elements.
(ii) The f-block elements are also called as rare earth elements. They are divided into lanthanoid series (4f block elements) and actinoid series (5f block elements).

IUPAC defines transition metal as an element whose atom has an incomplete d-sub shell or which can give rise to cations with an incomplete d-sub shell. They occupy the central position of the periodic table, between s and p-block elements.
Examples: Fe, Cu, Ag, Au

Cu, Ag and Au which have been used in making of coins in ancient times are called coinage metals

Chromium (24), the electronic configuration is 3d⁵4s¹. It ready to lose its outer most electron (4s¹) to get exactly half-filled stable electronic configuration. The electronic configuration of Zinc is 3d¹⁰4s².ie., It has completely filled stable configuration. From this configuration, the removal of 1e^- from 4s orbital is very difficult & it required more ionisation enthalpy. Due to this reason Zn has higher first Ionisation enthalpy (1.E₁) than that of chromium.

Electronic configuration of Ce⁴⁺ = [Xe] 4f⁰5d⁰6s⁰
Electronic configuration of Co²⁺ = [Ar]3d⁷

An interstitial compound or alloy is a compound that is formed when small atoms like hydrogen, boron, carbon or nitrogen are trapped in the interstitial holes in a metal lattice. They are usually non-stoichiometric compounds. Transition metals form a number of interstitial compounds such as TiC, ZrH_1.92, Mn₄N etc.
Properties of interstitial compound
(i) They are hard and show electrical and thermal conductivity.
(ii) They have high melting points higher than those of pure metals.
(iii) Transition metal hydrides are used as powerful reducing agents 
(iv) Metallic carbides are chemically inert.

Potassium dichromate is prepared from chromate ore (FeCr₂O₄). The ore is concentrated by gravity separation. It is then mixed with excess sodium carbonate and lime and roasted in a reverberatory furnace.

The roasted mass is treated with water to separate soluble sodium chromate from insoluble iron oxide. The yellow solution of Sodium Chromate is treated with concentrated Sulphuric acid which converts Sodium Chromate into Sodium dichromate.

The saturated solution of sodium dichromate is mixed with KCl and filtered, the filtrate is cooled to obtain K₂Cr₂O₇ crystals.
\(\begin{array}{cc} \mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}+2 \mathrm{KCl} & \rightarrow \mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}+2 \mathrm{NaCl} \\ \begin{array}{c} \text { Sodium dichromate } \\ \text { (orange red) } \end{array} & \begin{array}{c} \text { Potassium dichromate } \\ \text { (orange red) } \end{array} \end{array}\)

The fourteen elements following actinoids is from thorium to lawrencium are called actinides.
Examples: Uranium, Thorium, Neptunium