Difference Between d and f Block Elements

Main Difference – d vs f Block Elements

A chemical element is any material that cannot be broken down or changed by chemical means. There are 118 known chemical elements. These chemical elements are the building blocks of matter. All chemical elements are arranged in the periodic table of elements, in the order of increasing atomic number. There are also four groups of elements in the periodic table: s block, p block, d block and f block. Elements are grouped into these groups based on their electron configurations. For example, s block elements have their outermost electrons in an s orbital. p block elements have their outermost electrons in a p orbital. The main difference between d block elements and f block elements is that d block elements are chemical elements having electrons filled to their d orbitals whereas f block elements are chemical elements having electrons filled to their f orbitals.

Key Areas Covered

1. What are d Block Elements
– Definition, Chemical Properties
2. What are f Block Elements
– Definition, Chemical Properties, Lanthanides and Actinides
3. What is the Difference Between d and f block Elements
– Comparison of Key Differences

Key Terms: Actinides, Aufbau Principle, d Block, Electron Configuration, f Block, Inner Transition Elements, Lanthanides, Orbitals, Periodic Table

What are d Block Elements

d block elements are chemical elements having electrons filled to their d orbitals. The very first requirement for an element to be a d block element is the presence of d orbitals. Elements having at least one electron in their d orbitals are categorized as d block elements. The d-block of the periodic table is located between the s-block and the p-block.

One important fact about d block elements is that they have d orbitals that are partially or completely filled with electrons. According to Aufbau principle, electrons fill orbitals according to the ascending order of the energies of orbitals. In other words, electrons fill the ns orbital before filling the (n-1) d orbital. This is because the energy of ns orbital is lower than (n-1) d orbital. In elements of the first row of the periodic table, electrons first fill the 4s orbital before filling the 3d orbital.

Figure 1: Four Major Groups of the Periodic Table

But there are some exceptions as well. Although the energy level is lower, sometimes electrons fill the orbitals with the most stable electron configuration. For example, ns¹nd¹⁰ configuration is more stable than ns²nd⁹. That is due to the stability of the complete filling of the d orbitals. Such two examples are shown below.

Chromium (Cr) = [Ar]3d⁵4s¹

Copper (Cu) = [Ar]3d¹⁰4s¹

All d block elements are metals. They show very high melting points and boiling points due to their strong metallic bonds. The decreasing of the atomic radii is slight compared to that of s and p block elements. Moreover, the densities are very high due to the metallic nature. Due to the presence of d electrons, d block elements show variable oxidation states.

What are f Block Elements

f block Elements are chemical elements having electrons filled to their f orbitals. The f block is shown in the periodic table as a separate group at the bottom of the periodic table. That is because they have electrons filling up the f orbitals that are shielded by other orbitals; hence, f block elements are known as “inner transition elements”. The true position of the f block in the periodic table is between the s block and d block. These elements are known as rare elements because most of these elements are rarely found on earth.

There are two series of the f block elements named as,

Lanthanide series (elements are known as Lanthanides)
Actinide series (elements are known as Actinides)

These two series are named as such according to the element from which the series starts with. Lanthanide series starts immediately after Lanthanum (La) and actinide series starts with Actinium (Ac). All Lanthanides and Actinides are metals.

Difference Between d and f Block Elements

Figure 2: Lanthanides and Actinides

Lanthanide Series

Lanthanide series contains 14 elements that start immediately after Lanthanum. Therefore, this series contains a total of 15 elements along with Lanthanum. The atomic number of the series is from 57 to 71. They are known as “first inner transition series”. Lanthanides belong to the 4f series since these elements have their electrons filling to the 4f orbitals. But, Lanthanum has a completely empty f subshell; thus, the elements from Cerium (Ce) to Lutetium (Lu) are considered as the lanthanides.

The 4f electrons of these elements are completely shielded by other orbitals and do not take part in any chemical bonding. The Lanthanides are silvery-white metals and are good conductors of heat. The elements having completely or half-filled f orbitals are stable than other elements of the series.

The most stable oxidation state Lanthanides show is +3. Some elements show +2 and +4 oxidation states as well, but they are not stable as +3 oxidation state. Lanthanides are highly reactive and can react with elements such as hydrogen, oxygen, carbon, etc.

Almost all the ions formed by lanthanides are colourless. Lanthanides are electropositive elements. Therefore, they prefer to form molecules with electronegative elements. However, throughout the series, the changes of the chemical and physical properties are very less.

Actinide Series

Actinides are chemical elements that can be found in the actinide series of the f block in the periodic table of elements. All actinides are radioactive elements due to their unstable nature. These elements are composed of very large atoms. Actinides have their valence electrons in the 5f orbital. The actinide series is composed of chemical elements having the atomic numbers 89 to 103.

The most common and abundant actinides on earth are Uranium and Thorium. They are weakly radioactive and release high energy during radioactive decay. The prominent oxidation state among actinides is +3. In addition, actinides show oxidation states such as +4, +5 and +6.

Actinides form basic oxides and hydroxides. They have the ability to form complexes with ligands such as chlorides, sulfates, etc. Most complexes of actinides are colourful. However, due to the radioactivity and heavy metal behaviour, actinides are considered as toxic compounds.

Definition

d Block Elements: d block elements are chemical elements having electrons filled to their d orbitals.

f Block Elements: f block elements are chemical elements having electrons filled to their f orbitals.

Other Names

d Block Elements: d block elements are known as “transition elements”.

f Block Elements: f block elements are known as “inner transition elements”.

Oxidation States

d Block Elements: d block elements show a wide range of oxidation states depending on their electron configurations.

f Block Elements: The most stable oxidation state for f block elements is +3, and there can be other oxidation states as well.

Stability

d Block Elements: Almost all the elements in the d block are stable.

f Block Elements: Most f block elements are radioactive.

Groups

d Block Elements: d block elements can be either transition elements or non-transition elements.

f Block Elements: f block elements are in two series as Lanthanides and Actinides.

Electron Configuration

d Block Elements: d block elements have partially or completely filled outermost d orbitals.

f Block Elements: f block elements are unified by having one or more of their outermost electrons in the f orbital.

Conclusion

The periodic table of elements shows the arrangement of all known chemical elements according to their atomic numbers. There are four major groups of chemical elements that have similar chemical and physical properties among the members of each group. The d block and f block are two groups among those four groups. The main difference between d block elements and f block elements is that d block elements are chemical elements having electrons filled to their d orbitals whereas f block elements are chemical elements having electrons filled to their f orbitals.

Reference:

1. “General Properties and Reactions of The Actinides.” Chemistry LibreTexts, Libretexts, 21 Aug. 2017, Available here.
2. “Lanthanides: Properties and Reactions.” Chemistry LibreTexts, Libretexts, 20 Aug. 2017, Available here.
3. “f-Block Elements: Everything You Need to Know!” Toppr Bytes, 30 July 2017, Available here.

Image Courtesy:

1. “Periodic Table structure” By Sch0013r – File:PTable structure.png (CC BY-SA 3.0) via Commons Wikimedia
2. “Periodic table simple ca” By László Németh – Own work (CC0) via Commons Wikimedia [Cropped]