Why transition elements form a large number of complexes?
                d-block elements have a strong tendency to form complexes. This is because the cations of these elements have vacant d-orbitals, are small in size, have high ionisation energy, high heat of sublimation and low heat of salvation.
Why transition metals are known as d-block elements?
                Transition metals are known as d-block elements because the last electron in them enter the   (n-1) d-orbital’s, i.e. d-orbital of the penultimate shell.
Why do Zr and Hf exhibit similar properties?
This is because zr and Hf have almost same ionic sizes which is d nljkue to lanthanide contraction.
Why a transition series does contains 10-elements?
                There are five d-orbitals in an energy level and each orbital can accommodate two electrons. As we move from one element to the next, an electron is added to a d-orbital and for comlete filling of the five d-orbitals, 10 electrons are needed. Hence, each transition series contains 10 elements.
Why do transition elements show similarities along the horizontal period?
                Along a period, electrons are added into (n-1) d orbitals where as the outer shell electronic shell with reactant molecules.
Out of Cr2+ and Cr3+, which one is stable in aqueous solution?
                Cr3+ is more stable than Cr2+ in aqueous solutions. It is because of greater hydration enthalpy of Cr3+ ions due to its small size and higher charge.
Give an example of disproportionation reaction.
                Decomposition of copper (I) salt in water is an example of disproportionation reaction where half of the Cu (I) changes to copper metal and the other half to copper (II).
                      2Cu2+žCu+Cu2+
Which elements are called ferrous metals?
                The elements of the first triad of group 8, 9 and 10 i.e. iron, cobalt and Nickel are called ferrous metals.
What do you mean by 18 carat gold?
                An alloy of gold containing 18 parts by weight of pure gold, i.e. 75% gold and 255 copper is called 18 carat gold.
Why do transition elements have high value of hydration enthalpy?
                Transition elements have high value of hydration enthalpy due to their small size and higher charge.
Why do transition metals show variable oxidation states?
                It is because of the participation of inner (n-1) d electrons in bonding along with ns electrons.
Why are complex ions readily formed when water molecules react with the cation but not with hydronium ions?
                Water can easily donate a pair of electrons to the metal cation to form complex ions but hydronium ions due to the presence of positive charge are unable to form a bond with metal cation.

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