RBSE Class 12 Chemistry Notes Chapter 8 The d-and f-Block Elements
These comprehensive RBSE Class 12 Chemistry Notes Chapter 8 The d-and f-Block Elements will give a brief overview of all the concepts.
RBSE Class 12 Chemistry Chapter 8 Notes The d-and f-Block Elements
→ Cerium is the most occurring lanthanide. It exists about 3 * 10^% on earth crust. It is twenty sixth most abundant of all the elements.
→ Monazite sand is the most common mineral of lanthanides.
→ The JE° value of Ce4+/Ce is +1.74 V so it can oxidise water but the reaction is very slow, hence, Ce (IV) is a good analytical reagent.
→ Lathanides show limited number of oxidation states because the energy gap between of and 5d subshells is large.
→ It is very interesting to note that lanthanide ions with x/electrons have a similar colour to those with (14 - x)f electrons e.g., La3+ and Lu3+ are colourless. Sm3+ and Dy3+ are yellow and Eu3+ and Th3+ are pink.
→ Actinides show a large number of oxidation states. This is because of very small energy gap between 5/ 6d and 7s subshells. Hence all their electrons can take part in bond formation.
→ Th is used in atomic reactor and treatment of cancer.
→ U and Pu are used as fuel in nuclear reactor.
→ Misch metal (Ln = 95%, Fe = 5%, S, C, Ca, Al = traces). It is used in making based alloy. It is pysophoric alloy (emits spark when struck) used in making bullets, shells, ligher flints etc.
→ Actinides are silvery white metals. Their cations are coloured due to f-f transition.
→ The element, whose atom in ground state or ion in one of its common oxidation state has incomplete d-subshell, is known as transition element.
→ The general electronic configuration of transition elements is (n - 1)d1-10 ns1-2.
→ Tungsten (W) has the highest melting point among the d-block elements.
→ Technetium (Tc) is a synthetic transition element.
→ All transition elements are d-block elements but all d-block elements are not transition elements. For example group-12 elements i.e. Zn, Cd, Hg are not considered as transition elements yet they belong to d- block because they have completely filled (n - 1 )d orbitals and they do not show typical transition elements properties.
→ Group-3 elements i.e. Sc, Y, La, Ac are also differ from other transition elements as they do not show variable oxidation states. They show only +3 oxidation states. So their compounds are colourless and diamagnetic. From the above given reasons, group-3 and group-12 elements are called 'non-typical transition elements' while the rest are called 'typical transition elements'.
→ Ruthenium (Ru) and Osmium (Os) show highest oxidation state i.e. +8 in their compounds.
→ Transition metal compounds show isomorphism due to similarity in the size of their metal ions, e.g., FeSO4 . 7H2O and ZnSO4 .7H2O.
→ Transition metals are generally coloured both in solid as well as in aqueous state. The colour of compounds is due to presence of unpaired electron and d-d transition. The colour of some common ions are as follows:
→ The paramagnetism of transition metal ions can be calculated with the help of 'spin-only' formula
μ = \(\sqrt{n(n+2)}\) B.M. (where n = no. of unpaired electrons)
