Infamous Families of the Periodic Table

• Notable families of the Periodic Table and some important members:

1IA

18VIIIA

12

IIA13

IIIA14

IVA15VA

16VIA

17VIIA

2

33

IIIB4

IVB5

VB6

VIB7

VIIB8 9

VIIIB10 11

IB12IIB

4

5

6

7

Alkali

Alkaline (earth)

Transition Metals

Noble GasHalogen

Chalcogens

Periodic Table: The three broad Classes

Main, Transition, Rare Earth

• Main (Representative), Transition metals, lanthanides and actinides (rare earth)

groups 3-12 in which the d orbitals are progressively filled in each of the four long periods.The elements constituting the d-block are those in which the d - orbitals are progressively filled (incompletly filled ‘d’ orbitals

Position in the Periodic Table

THE TRANSITION ELEMENTS (d-BLOCK

The d–block occupies the large middle section flanked by s– and p– blocks in the periodic table. The very name ‘transition’ given to the elements of d-block is only because of their position between s– and p– block elements.

three rows of the transition metals, i.e., 3d, 4d and 5d. The

fourth row of 6d is still incomplete.

Electronic Configurations of the d-Block

electronic configuration (n-1)d1–10 ns1–2

Because of very little energy difference between (n-1)d and ns orbitals. case of Cr which 3d5 4s1 has instead of 3d4 4s2, Cu which has 3d 10 4s1 instead of 3d9s2

On what ground can you say that scandium (Z = 21) is a transition element but zinc (Z = 30) is not?

Silver atom has completely filled d orbitals (4d10) in its ground state. How can you say that it is a transition element?

Various precious metals such as silver, gold andplatinum and industrially important metals like iron, copper and titanium form part of the transition metals

Zinc, cadmium and mercury of group 12 have full d10configuration in their ground state as well as in theircommon oxidation states and hence, are not regardedas transition metals. However, being the end membersof the three transition series, their chemistry is studiedalong with the chemistry of the transition metals.

General Properties of the Transition Elements (d-Block)

1. Metallic properties such as high tensile strength, ductility malleability, high thermal and electrical conductivity and metallic lustre.

2. The transition metals (with the exception of Zn,Cd &Hg) are very much hard and have low volatility.

3.The d orbitals project to the periphery of an atom more than the other orbitals & exhibit certain characteristic properties a) variety of oxidation states, b) formation of colored ions c) complex formation with a variety of ligands d) catalytic property e) paramagnetic behaviour.

Physical PropertiesThe transition metals (with the exception of Zn, Cd and Hg) are very much hard and have low volatility. Their melting and boilingpoints are high

Involvement of greater number of electrons from (n-1)d in addition to the ns electrons in

the inter atomic metallic bonding.

melting points of these metals rise to a maximum at d5 except for anomalous values of Mn and Tc and fall regularly as the atomic number increases

Trends in enthalpies of atomization of transition elements

1. greater the number of valence electrons, stronger the inter atomic attraction, hence stronger bonding between atoms resulting in higher enthalpies of atomization.

2. metals of the second and third series have greater enthalpies of atomization than the corresponding elements of the first series

Enthalpy of atomization of zinc is the lowest, Why?

Variation in Atomic and Ionic Size

1.New electron enters a d orbital each time the nuclear charge increases by unity ,But the shielding effect of a d electron is not that effective, hence the net electrostatic attraction between the nuclear charge and the outermost electron increases and the ionic radius decreases

1.There is increase from the first (3d) to the second (4d) series of the elements. But the radii of the third (5d) series are virtually the same as 4d2.This is due to the intervention of the 4f orbital which must be filled before the 5d series of elements begin.

Lanthanoid contraction

There is a steady decrease in atomic radii from La due to the poor shielding of inner core electrons (4f) is known lanthanoid contraction.

Ionization Enthalpies

1. Due to an increase in nuclear charge there is an increase in ionisation enthalpy along each series of the transition elements from left to right.

2. Ionisation enthalpies give some guidance concerning the relative stabilities of oxidation states.

3.Although the first ionisation enthalpy, in general, increases, the magnitude of the increase in the second and third ionisation enthalpies for the successive elements, in general, is much higher.

4. Mostly IE1<IE2 <IE3 in each group

Why do IE1 of Cr is less ,but for Zn it is very high why for Zn IE2 is less

why for Fe IE3 is less , but for Mn it is very high

.

Oxidation States

1.The variability of oxidation states, a characteristic of transition elements2.They loose electron from ultimate and penultimate shell.3.oxidation state differ from each other by 1 unit(Fe+2, Fe+3) ,but in ‘P’ Block it differ by 2 unit(Sn+2, Sn+4) (due to inert pair effect)4. In Ni(CO)4 and Fe(CO)5, the oxidation state of nickel and iron is zero.(In π complex compound) ANSWER THE FOLLOWING 1. Name the element shows Largest number of oxidation state 2. Titanium (IV) is more stable than Ti(III) or Ti(II) 3. Name a transition element which does not exhibit variable oxidation states

1.Electrode Potentials value depends enthalpy of atomization ΔHa & hydration ΔH hyd2.The E0(M2+/M) value for copper is positive (+0.34V) high ΔHa and low ΔH hyd)

1.Why is Cr2+ reducing and Mn3+ oxidising when both have d4 configuration.

2.Cu, having a positive E0, accounts for its inability to liberate H2 from acids.

4. E0(M3+/M2+)valuesa) The low value for Sc reflects the stability of Sc3+

b) The highest value for Zn is due to the removal of an electron from the stable d10 configuration of Zn2+.c) Low value for Fe shows the extra stability of Fe3+ (d5).d) low value for V is related to the stability of V2+ (half-filled t2g e) The highest oxid. numbers are achieved in TiX4 ,VF5, CrF6 The ability of fluorine to stabilize the highest oxidation state isdue to either higher lattice energy as in the case of CoF3, or higher bond enthalpy terms for the higher covalent compounds, e.g., VF5 and CrF6

1. copper (I) compounds are unstable in aqueous solution and undergo disproportionation. 2Cu+ → Cu2+ + Cu

2.highest oxidation state of a metal exhibited in its oxide or fluoride(as they are more EN)

3.How would you account for the increasing oxidising power in the VO2+ < Cr2O72– < MnO4

Trends in Stability of Higher Oxidation States

MAGNETIC PROPERTY

PARAMAGNETIC DIAMAGNETIC FERROMAGNETIC

1. Diamagnetic substances are repelled by the applied field while the paramagnetic substances are attracted, attracted very strongly are ferromagnetic(ferromagnetism is an extreme form of paramagnetism)2. Many of the transition metal ions are paramagnetic.3. Paramagnetism arises from the presence of unpaired electrons,4. magnetic moment of an electron is due to its spin angular momentum and orbital angular momentum

5. magnetic moment is determined by the number of unpaired electrons and is calculated by using the ‘spin-only’ formula,

μ =√ n(n+2) n is the no. of unpaired electrons μ is the magnetic moment in units of Bohr magneton (BM). A single unpaired electron has a magnetic moment of 1.73BM

6. More the no. of unpaired electrons ,more the magnetic moment.

ANSWER THE FOLLOWING

1.Calculate the magnetic moment of a divalent ion in aqueous solution if its atomic number is 25.

2. Calculate the ‘spin only’ magnetic moment of M 2+(aq) ion (Z = 27).

Formation of Colored Ions

left to right: V4+, V3+, Mn2+, Fe3+, Co2+,Ni2+and Cu2+ • Color is due to excitation and reexcitation of unpaired‘d

electrons.• The frequency of the light absorbed lie in visible region• The color observed is the complementary color• The frequency depends on nature of ligand• In aqua complexes the color gets intensified

Formationof ComplexCompounds

• Metal ions bind a number of anions or neutral molecules giving complex

[Fe(CN)6]3–, [Fe(CN)6]4–, [Cu(NH3)4]2+ and [PtCl4]2–

. This is due to the • Comparatively smaller sizes of the metal ions,

• Their high ionic charges and

• The availability of d orbitals for bond formation.

Catalytic Properties

• ability to adopt multiple oxidation states and to form complexes (the activation energy is lowering)

EXAMPLESVanadium (V) oxide (in ContactProcess), finely divided iron (in Haber’s Process), and nickel (in Catalytic Hydrogenation)

Formation of Interstitial Compounds

when small atomslike H, C or N are trapped inside the crystal lattices of metals They are usually non stoichiometric

example, TiC, Mn4N, Fe3H, VH0.56 and TiH1.7

(i) They have high melting points, higher than those of pure metals.(ii) They are very hard, some borides approach diamond in hardness.(iii) They retain metallic conductivity.(iv) They are chemically inert.

Alloy Formation

Because of similar radii and other characteristics of transition metals,

The alloys so formed are hard and have often high melting points.

ferrous alloys: chromium, vanadium, tungsten, molybdenumand manganese are used for the production of a variety of steels andstainless steel.

Alloys of transition metals with non transition metalssuch as brass (copper-zinc) and bronze (copper-tin),