The key difference between lanthanide contraction and actinide contraction is that actinide contraction is greater than lanthanide contraction.
The term “contraction” in lanthanide contraction and actinide contraction refers to “the decrease in size” with increasing the atomic number. Therefore, lanthanide contraction is the decrease in size of an atom of a lanthanide with respect to the increasing atomic number while actinide contraction refers to the same phenomena with chemical elements in the actinide series.
CONTENTS
1. Overview and Key Difference
2. What is Lanthanide Contraction
3. What is Actinide Contraction
4. Side by Side Comparison – Lanthanide Contraction vs Actinide Contraction in Tabular Form
5. Summary
What is Lanthanide Contraction?
Lanthanide contraction is the decrease in the size of atoms with the increasing atomic number in the lanthanide series. It is a steady decrease in the atomic radius and the ionic radius of chemical elements in the lanthanide series. Further, this happens because of the filling of 4f orbitals with electrons before filling up the 5d orbital. Here, the 4f electrons show a poor shielding towards the nuclear charge, which in turn cause the 6s electrons to move towards the nucleus of the atom, resulting in a small radius.
Figure 01: Periodic Table
Moreover, this contraction is quite regular. The atomic numbers in the lanthanide series included in this contraction phenomena are from 57 to 71. The element having atomic number 71 is Lutetium, which has a smaller ionic radius than the chemical element having atomic number 72 in the subsequent series of elements.
What is Actinide Contraction?
Actinide contraction is the decrease in size of atoms with the increasing atomic number in the actinide series. The contraction here is a result of imperfect shielding of one 5f electron by another 5f electron of the same orbital. Thus, due to this poor shielding of the nuclear charge by 5f electrons, the effective nuclear charge increases, which leads to the contraction of the atom or decrease in the atomic size.
What is the Difference Between Lanthanide Contraction and Actinide Contraction?
Lanthanide contraction is the decrease in the size of atoms with the increasing atomic number in the lanthanide series while Actinide contraction is the decrease in size of atoms with the increasing atomic number in the actinide series. So, the key difference between lanthanide contraction and actinide contraction is that actinide contraction is greater than lanthanide contraction.
Below is an infographic that provides a summary of the difference between lanthanide contraction and actinide contraction.
Summary – Lanthanide Contraction vs Actinide Contraction
Basically, lanthanide contraction and actinide contraction are important terms regarding f block elements. These terms refer to the decrease of atomic size with increasing atomic number. The key difference between lanthanide contraction and actinide contraction is that actinide contraction is greater than lanthanide contraction.