Examples: The d and f Block Elements

The d and f block elements

The d-block of the periodic table includes groups 3 to 12. The elements placed in the group 3 – 12 are called d-block elements. In these elements, d-orbitals are progressively filled along with periods. f-block elements have been placed separately at the bottom of the periodic table.

The f-block includes those elements in which 4 f and 5 f orbitals are progressively filled. d-block elements are also called transition elements (or transition metals), and f-block elements are also known as inner transition elements (or inner transition metals).

Transition Metals

Transition elements or transition metals are those elements that have partially filled d-orbitals. Transition elements are also known as d-block elements. Transition elements occur from 21Sc to 112Cn, excluding lanthanides and actinides.

Lanthanide and actinides are known as inner transition elements. Transition elements show a transition from metals to nonmetals in the periodic table. That’s why, given the name transition elements. So, transition elements can be defined as the elements which are placed in between the s-block and p-block elements in the modern periodic table.

Properties of Transition Elements

Transition elements properties can be defined by the following points-

1. Transition elements show variable oxidation numbers and many valences. For example, Ti shows +3, +4 valences and Cr shows +2, +3, +4, +6 valances.

2. These elements form coordination compounds or coordination complexes.

3. These metals form coloured compounds.

4. These metals show high melting and boiling points.

5. These elements have high densities.

6. These elements show catalytic properties.

7. These elements generally form stable complexes.

8. These elements have a large charge and radius ratio.

Transition Elements Series

d-block elements or transition elements are divided into the following four series –

1. First Transition Series

2. Second Transition Series

3. Third Transition Series

4. Fourth Transition Series

1. First Transition Series – 1st transition series includes elements from Sc to Zn present in the 4th period of the periodic table.

2. Second Transition Series – 2nd transition series includes elements from Y to Cd present in the 5th period of the periodic table.

3. Third Transition Series – 3rd transition series includes elements from Hf to Hg present in the 6th period of the periodic table. The 6th period includes lanthanides also. Lanthanides are known as inner transition elements.

4. Fourth Transition Series Elements – 4th transition series includes elements from Rf to Cn present in the 7th period of the periodic table. The 7th period includes actinides also. Actinides are also known as inner transition elements.

Properties of Some Main Elements of d-block

Titanium – Titanium is the 7th most abundant metallic element and 9th most abundant element in the Earth’s crust. It is found chiefly as oxides in igneous rocks. It is also found in the lithosphere. Titanium is present in almost all living things, water bodies, rocks, and soil. For commercial use, titanium is mainly obtained by extracting ilmenite (FeTiO3) and rutile (TiO2) ores by mainly two processes, either Kroll process or Hunter process.

Vanadium – Vanadium is one of the most abundant metallic elements and the 20th most abundant element in the Earth’s crust. Vanadium has been detected in the light from the Sun and some other stars. Pure vanadium is rare in nature, but almost 65 various compounds occur naturally.

For commercial use, vanadium is mainly obtained by extraction of patronite (VS4) ores. It is also found in crude oil, coal, oil shale (Sedimentary rock), tar sands deposits, and bauxite ore. It is mainly produced directly from magnetite or heavy oil. It is also obtained as a byproduct of uranium mining. It is produced from steel smelter slag in China and Russia.

The f-block Elements or Inner Transition Elements

f-block includes lanthanoids (4f elements; Ce to Lu) and actinoids (5f elements; Th to Lr).

The Lanthanides

These elements have an electronic configuration with 6s2 common but with variable occupancy in 4f – orbitals.

Properties of Lanthanides

The lanthanoid contraction – As we move from lanthanum to lutetium, a decrease in atomic and ionic radii is observed. This is called lanthanoid contraction.

• Elements of the lanthanide series have a silvery appearance and have lustre.

• All these elements are soft and can be cut by a knife.

• Some elements of the series are very reactive, while others are less reactive.

• They have high melting and boiling points.

• They react with hydrogen and release energy.

• They are strong reducing agents.

• They react with many nonmetals and form binary compounds.

• Lanthanides show high coordination numbers such as 8, 9, 10, or 12, etc.

The Actinides

The actinide series includes 14 elements from Thorium to Lawrencium. These elements have an electronic configuration with 7s2 common but with variable occupancy in 5f and 6d subshells.

Properties of Actinides

• All elements of the actinide series are radioactive.

• These elements are electropositive.

• These metals get spontaneously ignited in the air.

• Many allotropes of these elements can be formed. For example, Plutonium has 6 allotropes.

• These metals are also soft, like lanthanides.

• They also react with many nonmetals.

• Many elements of this series exhibit properties of both d-block and f-block elements.

Neptunium: An important Element of the Actinide Series

Neptunium is the 1st synthetic transuranium metal. Many false claims were made for its discovery. But the 1st time, it was first synthesised by American physicists Edwin McMillan and Philip H. Abelson at Berkeley Radiation Laboratory in 1940.

Edwin McMillan got the Nobel prize for synthesising the transuranium element. They used uranium to synthesise the neptunium element. They prepared a larger sample of bombarded uranium and showed the following reaction –

92U238 + 01n → 92U239β-(23 min)→ 93Np239β- (2.3 days)→ 94Pu239

Neptunium is named after the planet Neptune. According to Roman mythology, Neptune is a god of the sea. The word is taken from the Latin word Neptunus, and Neptune is identified with the Greek god Poseidon.

Neptunium is not found in pure elemental form in nature as it is a synthetic element and forms by the nuclear reaction of uranium. It generally forms a green coating of its oxide when exposed to moist air. It is a hard, ductile, radioactive, and silvery-colored actinide metal.

Neptunium is found in its three allotropic forms – 𝛼 – neptunium, β – neptunium, and 𝛾 – neptunium. All three allotropes of neptunium show different symmetry in structure. 𝛼 – neptunium has an orthorhombic structure, β – neptunium has a tetragonal structure, and 𝛾 – Neptunium has a body-centred cubic structure. It has almost 24 isotopes. Out of 24 isotopes, neptunium -237 is highly stable with a half-life of 2.14 x 106 years. Its synthetic isotope neptunium 236 is also very stable with a half-life of 1.54 x 105 years.

Conclusion

The middle layer in the periodic table is filled with the d block elements. The inner d orbits of groups 3 to 13 are progressively filled. On the other side, the f block elements are found outside and at the bottom of the periodic table. In these elements, the 5f and 4f orbitals are progressively filled. The 3 series of transition elements are recognised by the filling of 3d, 4d, and 5d orbitals. They hold a high boiling and melting point.