The elements in the middle of the periodic table, from Group 3 to 12, are referred to as d-block elements. The name d-block comes from the fact that the final electron enters the d-orbital of the penultimate shell. These are frequently referred to as transition elements because their properties fall in between highly reactive metallic s-block elements and nonmetallic p-block elements. The d block contains four series that correspond to the filling of 3d, 4d, 5d, or 6d orbitals.

In general, a transition element is any element that corresponds to the d-block of the modern periodic table (groups 3-12). Lanthanides and actinides, which are f-block elements, can also be categorized as transition metals. However, because f-block elements contain partial f-orbitals, they are also known as inner transition elements or inner transition metals.

General Properties of Transition Elements

The electron configuration corresponds to (n-1)d⁵ ns¹ or (n-1)d¹⁰ ns¹. This is due to the stability offered by electron orbitals that are half-full or totally filled. Zinc, cadmium, and mercury are not considered transition elements because their electrical configurations differ from those of other transition metals. The properties of the remaining d-block elements, on the other hand, are quite similar, and this likeness may be seen down each row of the periodic table.

The properties of the second and third-row elements gradually change as we move from left to right along the periodic table. The outer shells of these elements have poor shielding properties, which raises the effective nuclear charge as more protons are added to the nucleus. The characteristics of the transition elements are listed below.

• When these elements mix, they form colorful compounds and ions. The electron d-d transition explains its color.
• The energy difference between these elements’ possible oxidation states is modest. As a result, transition elements have a wide range of oxidation states.
• These elements produce a huge number of paramagnetic compounds due to the unpaired electrons in the d orbital.
• A vast variety of ligands can bind to these elements. As a result, transition elements produce a diverse array of stable complexes.
• The charge-to-radius ratio of these elements is very high.
• Transition metals are hard and have relatively high densities when compared to other elements.
• Because delocalized d electrons engage in metallic bonding, these elements have high boiling and melting temperatures.
• The transition elements are also good conductors of electricity due to the metallic bonding of the delocalized d electrons.

Position in Periodic Table: The d and f – block Elements

The study of which elements are in a specific group position in the periodic table is important for comprehending such elements as a whole. There is a reason why different elements in the periodic table are classified. The d and f block components have certain features that qualify them for this category.

The d-block elements are made up of elements created by electrons filling shells 3d, 4d, and 5d. They are also known as transition elements since their periodic table position is between the s-block and p-block elements. Their properties are transitional between the extremely reactive metallic elements of the s-block, which often form ionic compounds, and the predominantly covalent elements of the p-block.

D-block elements or transition elements are those elements or ions that have partially filled d sub-shell or those elements in which the differentiating electrons occupy (n-1) d sub-shell. They have named transition elements because their attributes reveal a transition from the left side (s-block) elements to the light side (p- block elements). There are four d-series, each beginning with (n-1)d¹ ns² and ranging from group 3 to group 12. (or group IIIB to II B).

In the d-block, electrons are added to the penultimate shell, increasing its size from 8 to 18. Typically, transition elements have an unfinished d level. Group 12 (zinc) has a d¹⁰ configuration, and because the d shell is complete, compounds of these elements are unusual and differ from the others. The elements are divided into three complete rows of ten elements each, as well as an incomplete fourth row. The f-block parts are used to discuss the position of the unfinished fourth series. These elements include precious metals such as silver, gold, and platinum, as well as industrially vital elements such as iron, copper, and nickel.

Position of transition metals in the periodic table

• Inner transition elements are another term for ‘f’ – block elements. In these elements, the last electron normally enters the orbital’s penultimate, i.e. (n – 2) f. The distinguishing electron in transition elements can enter either 4f or 5f orbitals, allowing them to be further classified as lanthanides or actinides.
• The differentiating electron in lanthanides reaches the 4f orbital. These range from cerium to lutetium. Lanthanides are named for the elements that come directly the following lanthanum. The differentiating electron in actinides enters the 5f orbitals. Typically, they are thorium to lawrencium.
• In the periodic table, these elements appear shortly the following actinium. (n–2) f^1–14(n–1) d^0–1ns2 is the general electronic configuration of f – block elements. Lanthanides have an electronic configuration of [Xe]4f^1–145d^0–16s², whilst Actinides have an electronic configuration of [Rn]5f^1–146d^0–17s².

Sample Questions

Question 1: What are the transition metals’ metallic properties?

Answer:

Malleability, ductility, high tensile strength, and metallic lustre are all characteristics of transition metals. They are good heat and electrical conductors and have a tendency to crystallise. Trends in the metallic properties of transition elements, on the other hand, are visible. Elements such as chromium and molybdenum are among the hardest transition metals because they contain a large amount of unpaired electrons.

Question 2: Why are all the transition elements metals?

Answer:

All transition elements are metals because their outermost shells contain only two electrons. Because of the strong metallic linkages, they are also malleable, durable, and ductile.

Question 3: How do the d-block elements differ from f-block elements?

Answer:

The last electron in the d-block enters the d-orbital of the penultimate shell. The electron enters the f-orbital of the anti-penultimate shell in the f-block elements. The oxidation state of d-block elements varies, whereas the oxidation state of most f-block elements is +3. Almost all d-blocks are stable, whereas a greater proportion of f-blocks are radioactive.

Question 4: What are the catalytic properties of transition elements?

Answer: 

Because of the presence of unoccupied d-orbitals, the tendency to exhibit fluctuating oxidation states, the ability to generate reaction intermediates with reactants, and the presence of defects in their crystal lattices, transition elements exhibit catalytic capabilities.

Question 5: Why do d – Block Elements have high Melting and Boiling Points?

Answer:

In addition to metallic bonding by s-electrons, unpaired electrons and vacant or partially full d-orbitals produce covalent bonds. D-block elements have higher melting and boiling temperatures than s and p block elements due to their strong bonding. This trend continues until the d5 configuration, at which point it begins to decline as more electrons are coupled in the d-orbital.