F Block Elements On The Periodic Table | Introduction

Updated on 30 August 2022

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Updated on 30 August 2022

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F block elements of the periodic table are found in two series, namely Lanthanoids and Actinoids. Lanthanides are also known as rare earth metals. F block elements are also known as inner transition metals as they provide a transition in the sixth and seventh row of the periodic table.

What Are F Block Elements?

F block elements are those elements of the periodic table whose deep-seated 4f and 5f orbitals are filled with electrons with increasing atomic numbers. F block elements are placed at the bottom of the periodic table. They are a subset of the sixth and seventh periods.

Given below is a list of F block elements

Lanthanum (La)
Cerium (Ce)
Praseodymium (Pr)
Neodymium (Nd)
Promethium (Pm)
Samarium (Sm
Europium (Eu)
Gadolinium (Gd)
Terbium (Tb)
Dysprosium (Dy)
Holmium (Ho)
Erbium (Er)
Thulium (Tm)
Ytterbium (Yb)
Lutetium (Lu)
Actinium (Ac)
Thorium (Th)
Protactinium (Pa)
Uranium (U)
Neptunium (Np)
Plutonium (Pu)
Americium (Am)
Curium (Cm)
Berkelium (Bk)
Californium (Cf)
Einsteinium (Es)
Fermium (Fr)
Mendelevium (Md)
Nobelium (No)
Lawrencium (Lw)

Tips - How to learn the periodic table

Types Of F Block Elements

Lanthanoids: The first series of elements in the F block starts with the element Lanthanum, which has the atomic number 51. The elements with atomic numbers 57 to 71 are lanthanoids. Lanthanides are non-radioactive except for promethium which is radioactive.

Actinoids: The second series of elements in the f block start with Actinium which has the atomic number 89. The elements with atomic numbers 89 to 103c are actinoids. Actinides are usually radioactive.

Properties of F Block Elements

F block elements have electrons added to the f suborbital of the (n - 2) level.
F block elements are placed between (n - 1)d and ns block elements.
Many properties of F block elements are similar to D block elements.

Let us look at the properties of lanthanoids and actinoids separately.

Properties Of Lanthanides

They are soft metals with a light silver colour
When exposed to air, these metals become dull
Melting points of these metals ranges from 1000k to 1200k, except for samarium, which has a melting point of 1623k
These elements are good conductors of heat and electricity
These elements are non-radioactive in nature except for promethium
The ionic and atomic radii decrease from lanthanum to lutetium. This is called the lanthanoid contraction.

Properties of Actinides

These elements have a silvery colour
These elements usually have a radioactive nature
These metals are highly reactive and their reactivity increases when finely divided
The ionic and atomic radii decrease from actinium to lawrencium. This is called actinoid contraction.
These elements generally have an oxidation state of 3+

Difference Between Lanthanoids and Actinoids

Lanthanides are involved in the filling of 4f orbitals whereas actinides are involved in the filling of 5f orbitals
The binding energy of 4f electrons is lesser than the binding energy of 5f electrons
The shielding effect of 4f electrons is comparatively more effective than 5f electrons
It is easy to determine the paramagnetic properties of lanthanoids but it is difficult to determine the same for actinides
Lanthanides are non-radioactive except promethium whereas all actinides are radioactive in nature.
Lanthanoids do not have a tendency to form oxidations whereas actinides form several oxycations
Compounds of lanthanides are less basic whereas compounds of actinides are highly basic.

Similarities Between Lanthanoids and Actinoids

Both lanthanoids and actinoids have an oxidation state of 3+
Both lanthanoids and actinoids are involved in the filling of (n-2) f orbital
Both lanthanoids and actinoids are highly electropositive and highly reactive in nature
With an increase in atomic number, the atomic and ionic sizes of both lanthanoids and actinoids decreases
Both lanthanoids and actinoids show magnetic properties

This is a brief description of the F block of the modern periodic table. Happy Learning!

IIT Entrance Class 12 (PCM) Sciences