CHAPTERCHAPTER- 8
d--and ff--block Elements
The d
Gold is considered to be the king of metals.
Gold is soluble in mercury.
The nobility of metals increases with increase in atomic number from Cu to Au.
Ag, Cu andd Au are coinage metals and their reactivity decreases in the order Cu > Ag >
Au
Fulminating Gold : It is Au (NH2) = NH or N2H3.
Purple of Cassuis is a colloidal solution of gold.
Purity of gold is expressed in fineness or carat. Pure gold is 24 carats.
Mercury is the only liquid metals at room temperature.
Mercuric salts are more stable than Mercurous salts.
Mercury forms alloys (called Amalgam) with all metals axcept iron and platinum. Hence
mercury is transported in iron containe
containers.
Scandium (Z = 21) does not exhibit variable oxidation states.
Ex - Why is Cr2+ reducing and Mn3+ oxidizing when both have d4 configuration.
Solution- Cr2+ is reducing as its configuration changes from d4 to d3, the latter having a
half-filled t2g level (see Unit 9). On the other hand, the change from Mn2+ to Mn3+ results
in the half-filled (d5) configuration which has extra stability.
Highest oxidation state shown by any transition element is +8 (Ru in 4d-series and Os in
5d-series).
Mn shows maximum state of +7 in KMnO4.
Magnetic property of transition metal depends upon he number of unpaired electrons in
d-orbitals. Metals with five unpaired electrons e.g., Mn have maximum paramagnetic
character.
Fe2+ is green and Fe3+ is yellow.
Fe3+ is powerful oxidizing agent than Fe2+ ion.
Iron is rendered passive by conc. HNO3 and other oxidizing agents like K2Cr2O7,
KMnO4, chloric acid, chromic acid, silver nitrate etc. A specimen of passive iron can be
rendered active by scratching the film mechanically or chemically (e.g., immersing in
conc. Alkali solution, heating in reducing atmosphere of H2 or CO).
FeCl3 is used as stypic to stop bleeding from a cut
Iron carbide or cementite is Fe3C.
Kipp’s base in FeS + H2SO4.
When a particular oxidation state become less sable relative to other oxidation states, one
lower. One higher, it is said to undergo disproportionation. For example, manganese (VI)
becomes unstable relative to manganese (VII) and manganes (IV) in acidic solution.
3 mnvio4 2- + 4 H+ → 2 mnvii O-4 + mnivo2 + 2H2O
Ex - Name a member of the lanthanoid series which is well known to exhibit +4
oxidation state.
Solution- Cerium (Z = 58)
AgCl, AgBr and AgI are insoluble in water. It is due to high lattice energy of these
compounds AgF is soluble in water. It is due to large hydration energy of ‫ ି ܨ‬ion.
First member of each transition series i.e., Sc, Y, La and Ac do not show variable
valency. They show only +3 oxidation state.
Transition metal highest melting point is W and transition metal with lowest melting
point is Hg.
The only synthetic transition metal is Tc. The only man made lanthanide is Pm.
Fe, Co and Ni are called ferrous metals. They are all strongly attracted by a magnetic and
are ferromagnetic.
Ru, Rh, Pd, Os, Ir and Pt are called platinum metals.
Cu, Ag and Au are called coinage metals.
Cu2+ is more stable than Cu+ in aqueous solution. This is due to extensive hydration of
Cu2+ due to smaller size and higher charge.
A mixture of TiO2 and BaSO4 is used as a white pigment under the name Titanox.
Another white pigment is lithophone- a mixture of ZnS and BaSO4.
The d-block consisting of Group 3-12 occupies the large middle section o the periodic
table. In these elements the inner d orbital are progressively filled.
The f-block is placed outside at the bottom of the periodic table and in the elements of
this block 4f and 5f orbital are progressively filled.
The transition elements vary widely in their chemical behavior. Many of them are
sufficiently electropositive to dissolve in mineral acids, although a few are noble’. Of the
first series, with the exception of copper, all the metals are reactively reactive.
The transition metals react with a number of non-metals like oxygen, nitrogen, sulphur
and halogens to form binary compounds.
The two series of inner transition elements, lanthanoids and actinoids constitute the fblock of the periodic table.
With the successive filling of the inner orbital. 4f, there is a gradual decrease in the
atomic ad ionic sizes of these metals along the series (lanthanide contraction).
Transition elements lie between electropositive s-block elements and electronegative pblock elements in the periodic table.
In representative elements (s and p-block elements) the valence electrons are present only
in the outermost shell while in transition elements, the valence electrons are present in the
outermost shell as well as d-orbitals of penultimate shell.
All transition elements are d-block elements, but all d-block elements are not transition
elements.
The transition elements show both covalent as well as metallic bonding amongst their
atoms.
The d-block elements do not form ionic compound so readily as the alkali and alkaline
earth metals.
Unlike the s-block elements, the d-block elements have a tendency to form covalent
compounds under certain conditions.
Generally, lower valent compounds are ionic while the higher valent compounds are
covalent
Zn, Cd, Hg are colorless and are diamagnetic.
Many transition metal compounds are isomorphus e.g., FeSO4.7H2O and ZnSO4.7H2O
because of almost equal ionic sizes of these metals.
Transition elements like Se, Y, La and Ac donot show variable valiancy.
Lightest transition metal is Sc (density 3.1 g cm-3) and heaviest and densest transition
elements is osmium.
When the metals like Fe, Co, Ni are placed in magnetic field, their magnetic domains are
turned so that all points in the same direction given rise to a large magnetic effect. Such
substances are known as ferromagnetic.
The reactivity of transition elements decreases with the increase in their atomic number.
Cu+ with d10 configuration should be stable but actually Cu2+ ion is more stable than Cu+
ion because of increased hydration.
All the elements of 3d-series are good reducing agents except copper.
Mercurous ion exist as dimer ‫݃ܪ‬ଶଶା and not as Hg+ and this explains its diamagnetic
nature.
Platinum is inert (or noble metal) but it dissolves in aqua regia due to the formation of
H2PtCl6.
TiCl4 and TiO2 are used in smoke screens.
Mo is used in X-ray tube, Ta in analytic weights and instruments used in surgery of veins.
Most abundant and most widely used transition metal is iron.
Zinc metal is brittle and hard at room temperature.
Mercury is the only liquid metal at room temperature.
FeSO4 is used in manufacture of blue black ink.
Slag is formed only by ferrous oxide ( FeO ), ferric oxide (Fe2O3) does not form a slag.
Copper dissolves in an aqueous solution of FeCl3.
Mohr’s salt in resistant to atmospheric oxidation.
When a little of mercury is poured into a AgNO3 solution, a tree like growth of silver
amalgam is produced. This is called Mercury tree.
Mercuric chloride or Corrosive sublimated is HgCl2. It is poisonous and best antidote for
it is white of an egg.
Alkaline solution of K2HgI4 is called Nessler’s reagent and gives brown precipitate
[HgI.HgO.NH2 or iodide of million’s base] with ammonia.
A piece of copper readily dissolves in a solution of FeCl3. This is because E0Fe3+/Fe2+ is
more than E0Cu2+ /Cu.
Cu(s) + 2FeCl3 (aq) → 2FeCl2(aq) + 2CuCl2(aq)
This method is used for making printed circuited circuit boards (P.C.Bs) used in
electronic industry.
A finely powdered form of Fe2O3 is called Jeweller’s rouge. It is used for polishing
Jewellery.
Turnbull’s blue is Fe3[Fe(CN)6]2 obtained by adding Fe2+ ions to potassium ferricyanide,
K3[Fe(CN)6] solution.
Prussian blue is potassium ferric ferricyanide [KFe(III)] [Fe(II) (CN)6]. It is obtained by
adding Fe3+ ions to potassium ferricyanide K4[Fe(CN)6] solution.
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