SOLVED N.C.E.R.T. TEXTBOOK EXERCISES
Silver atom has completely filled d- orbitals ( 4d10) in its ground state. How can you say that it is a transition elements
According to definition , transition elements are those which have partially d- subshell in their elementary state or in their one of the oxidation states
In the series (Z is equal to 21) to Zn(Z is equal to 30), the enthalpy of Zinc is the lowest (126KJ mol-1) .Why
The high enthalpies of atomization of transition elements is due to the participation of electrons (n-1) d-orbitals in addition to ns electrons in the interatomic metallic bondings.
Which of the 3rd series of the transition metals exhibits the largest number of oxidation states and why
MN (Z=25) exhibits the largest number of oxidation states because it has the maximum number of unpaired elecrtons. Hence, it shows oxidation states from +2 to +7.
How would you account for the irregular variation of ionisation enthalpies (first and second) in the first series of transition elements
The irregular trend in variation of ionization enthalpies in the first series of transition elements is because of varying degree of stability of different configurations.
Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only
Because oxygen and fluorine have small size and high electronegativity, therefore, they can easily oxidize the metal to its highest oxidation state.
Which is a stronger reducing agent Cr2+ or Fe2+ and why
Cr2+ is a stronger reducing agent than Fe2+.This is because the configuration of Cr2+ changes from d4 to d3 and d3 configuration is stable (t2g3) being half filled together level.
Explain why Cu2+ ion is not stable in aqueous solution
Cu2+ (aq) is not stable in aqueous solution because of its less negative enthalpy of hydration than of Cu2+.
D BLOCK ELEMENTS
The atomic radii of elements of a particular series decreases with increase in atomic number but this decrease in atomic radii becomes small after midway.
The ionic radii decrease with increase in oxidation state.
All these metals of d block have high density. Within in a period ,the densities of these metals vary inversely with the atomic radii.
Melting and Boiling points
The melting points of these metals rise to a maximum value and then decrease with increase in atomic number . But manganese and technetium metals have abnormally low melting points.
The first ionisation enthalpies of d-block elements are higher than those of s-block elements but are lesser than those of p-block elements. The ionisation of enthalpies increase as we move across each series,though not quite regularly.
With the exception of a few elements, most of these show variable oxidation states.