d and f block elements class 12 notes
These elements are found in the periodic table’s middle layer. The inner d orbits of groups 3–13 are gradually filled. The f block elements, on the other hand, are located outside and at the bottom of the periodic table. In these elements, the orbitals of the 5f and 4f get filled in.
The filling of 3d, 4d, and 5d orbitals distinguish the three transition element series. They have a high melting and boiling point.
The metallic characteristics shown by the transition elements are as follows:
Thermal conductivity, electrical conductivity malleability, high tensile strength, metallic strength, and ductility.
There are three transition series of ten components each:
(i)The first transition series includes the filling of 3d-orbitals. It begins with scandium (Z = 21) and progresses to zinc (Z = 30).
(ii) The second transition series entails the filling of 4d-orbitals. It begins with yttrium (Z=39) and progresses to cadmium (Z=48).
(iii) The third transition series entails the filling of 5d-orbitals. Lanthanum (Z = 57) is the first element in this series. It is followed by 14 elements known as lanthanides, which fill 4f-orbitals. The following nine elements in the third transition series range from hafnium (Z = 72) to mercury (Z = 80).
Inner-transition elements are f-block elements. A transition element has partially filled d orbitals in its ground state or any of its oxidation states. Because of their filled d – orbitals, zinc, cadmium, and mercury are not considered transition metals.
The f-Block elements: The f-block elements are those in which the 4 f and 5 f orbitals are gradually filled in the last two long periods.
Lanthanoids: Lanthanoids are the 14 elements that come after lanthanum, from Cerium (58) to Lutetium (71). They are part of the first inner transition series. Lanthanum (57) possesses comparable qualities. As a result, it is being researched alongside lanthanoids.
Actinoids are the 14 elements that come after actinium (89), with atomic numbers ranging from 90 (Thorium) to 103 (Lawrencium). They have the belonging to the second inner transition series.
There are four transition series:
1) Transition series in 3D. The first transition series consists of transition elements with atomic numbers ranging from 21 (Sc) to 30 (Zn) and possessing incomplete 3d orbitals.
2) 4d – a succession of transitions It is made up of elements with atomic numbers ranging from 39 (Y) to 48 (Cd) and with incomplete 4d orbitals. It is known as the second transition series.
3) 5d – sequence of transitions It is made up of elements with atomic numbers ranging from 57 (La) to 80 (Hg) and incomplete 5d orbitals. It is known as the third transition series.
4) 6d – sequence of transitions It is made up of elements with atomic numbers ranging from 89 (Ac), 104 (Rf), to 112 (Uub) and incomplete 6d orbitals. It is known as the fourth transition series.
General Properties of d and f block elements
All transition elements are metallic, strong conductors of heat and electricity, and exhibit a steady decline in electropositive character as they progress over a period. These metals are hard, have high densities, high enthalpies of atomization, high melting and boiling temperatures, and form alloys with other metals due to strong metallic bonding. There are a few more sub-points mentioned below:
- Melting Point: The melting point of these initially rises to its maximum, then progressively falls towards the conclusion of the sequence. Metallic bond strength is proportional to the number of half-filled d-orbitals.
- Atomic Radius: The radii of ions in a particular series with the same charge and magnitude decrease gradually as the atomic number increases. This is due to the d-electrons’ weak shielding effect.
- Ionisation Energy: Transition elements have greater ionization energies. er than s-block elements but less than p-block elements In the series, it normally increases from left to right.
- Oxidized States: Transition metals have a wide range of oxidation states. The varied oxidation states of transition metals are caused by the bonding of ns and (n – 1)d- electrons.
- Reaction with Acids: The majority of transition metals are electropositive. When they react with mineral acids, they produce H2 gas.
- Magnetic Properties: Many transition elements and their compounds are paramagnetic. Because most transition metals are paramagnetic, they produce colored compounds due to the presence of unpaired electrons. It increases from Sc to Cr and subsequently drops because the number of unpaired electrons increases from Sc to Cr and then decreases because the number of unpaired electrons rises from Sc to Cr and subsequently falls. They are rarely diamagnetic.
- Lanthanoid Contraction: The gradual reduction in the atomic and ionic radii of transition metals as atomic number increases. This is due to the 4f orbitals being filled before the 5d orbitals. This size contraction is pretty regular. This is referred to as lanthanoid contraction. The atomic radii of the second row of transition elements are nearly identical to those of the third row of transition elements due to lanthanoid contraction.
- Another typical property of transition metals is the formation of colored compounds (both in solid form and in aqueous solution). This is due to the absorption of some visible light radiation, which causes the d-d transition of electrons in transition metal atoms.
- In contrast to s- and p-block components, transition elements can form complexes. This is because these elements (a) have tiny highly charged ions and (b) have unoccupied d-orbitals.
- Many transition metals and their derivatives serve as catalysts in a wide range of processes.
- A significant number of interstitial compounds are formed by transition metals.
- Transition metals are responsible for the formation of a vast number of alloys. It is because their atoms can easily swap places in their metal crystal lattices.
- Transition metal oxides in lower oxidation states are often basic, whereas those in higher oxidation levels are amphoteric or acidic.
Lanthanide properties in d and f block elements
- The general electrical configuration is [Xe] 4f1-14 5d0-1 6s2.
- The metals have a silvery-white appearance. They are malleable, ductile, have low tensile strength, and are good heat and electricity conductors.
- They are quite dense and have high melting points.
- Lanthanides have a primary oxidation state of + 3. Some elements, however, have + 2 (Eu2+) and + 4 (Ce4+) oxidation states.
- The electronic transition between distinct four f-levels colors several lanthanide ions.
- The presence of unpaired electrons causes paramagnetism in the bulk of lanthanide ions. La3+ and Ce4+ are examples of lanthanoid ions that do not show paramagnetism because they lack 4f-electrons or have a full 4f-level. For example, Yb2+ and Lu3+.
- Lanthanides quickly tarnish in air and soil, producing trioxides (except cesium, which forms Ce02).
- Lanthanide oxides and hydroxides have basic properties.
- Lanthanoid chemicals are primarily ionic. Lanthanoid contraction refers to the steady decrease in atomic size that occurs over the first f- transition element series.
Actinides properties in d and f block elements class 12 notes
- The general electronic configuration is [Rn] 5f0-14 6d s0-1 7s2.
- All of the elements are silvery-white metals.
- The actinides have somewhat high melting points.
- The actinides’ ionic size diminishes steadily along with the series.
- Actinides can exist in a variety of oxidation states. Actinides, on the other hand, prefer the +4 oxidation state.
- Some actinoid elements, such as uranium, neptunium, and plutonium, can exist in the + 6 oxidation state.
- A large number of actinoid elements are radioactive. Beyond uranium, all elements are man-made.
- Actinides are substantially more likely than lanthanides to form complexes.
Also Read – p Block Elements class 12 Notes
Conclusion – d and f block elements class 12 notes
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