Lanthanide Contraction – Everything You Need to Know About

Lanthanide Contraction – Everything You Need to Know About

Lanthanide Contraction is one of the interesting exceptions to study in the Chemistry subject.

Sometimes, it is also known as the Lanthanoid Contraction.

It applies to the elements in the Lanthanide Series of the Periodic Table. Lanthanide series ranges from atomic number 57 to atomic number 71.

In this blog post, Like the d-block contraction, I will be talking also about the Lanthanide or Lanthanoid Contraction in detail.

So, here we go…

✅Recommended read: Polyvinyl Alcohol – Everything You Need to Know About

What is Lanthanide Contraction?

Sudden decrease of the ionic radii of the elements of the periodic table in the Lanthanide Series is called the lanthanide contraction.

According to Wikipedia,

The lanthanide contraction is the greater-than-expected decrease in ionic radii of the elements in the lanthanide series from atomic number 57, lanthanum, to 71, lutetium, which results in smaller than otherwise expected ionic radii for the subsequent elements starting with 72, hafnium.

So, in this contraction, with the increase in the atomic number, size of atoms and ions from Lanthanum (atomic no. 57) through Lutetium (atomic no. 71) decreases more than the expected value.

Lanthanide Contraction Ionic Radii Graph
Image Source

 

This contraction was discovered by the Norwegian geochemist named Victor Goldschmidt.

How many Elements of the Periodic Table does Lanthanide Contraction Apply to?

Well, as mentioned above, it applies to the elements of the lanthanide series only. And, there are a total of 14 elements in the series.

All the 14 elements of the series are:

Atomic Number Element Element (Full Name) Ln3+ radius (pm)
(6-coordinate)
57 La Lanthanum 103
58 Ce Cerium 102
59 Pr Praseodymium 99
60 Nd Neodymium 98.3
61 Pm Promethium 97
62 Sm Samarium 95.8
63 Eu Europium 94.7
64 Gd Gadolinium 93.8
65 Tb Terbium 92.3
66 Dy Dysprosium 91.2
67 Ho Holmium 90.1
68 Er Erbium 89
69 Tm Thulium 88
70 Yb Ytterbium 86.8
71 Lu Lutetium 86.1

Download the PDF of List of All Elements of Lanthanide Series

Lanthanide Series 14 Elements
Image Source

 

What Causes Lanthanide Contraction

6s electrons are drawn towards the nucleus due to the poor shielding of nuclear charges by 4f electrons. The movement of the 6s electrons towards nucleus results in the smaller atomic radius.

Shielding effect is also known as the atomic shielding or electron shielding which explains the attraction between an electron and the nucleus inside a multi-electron atom.

Effects on the Lanthanides

Due to this lanthanoid or lanthanide contraction, outer shell electrons are more attracted towards the nucleus across the lanthanides which results in considerably smaller ionic radii.

This contraction also affects the post-lanthanide series elements of the periodic table.

Effects on the Post-lanthanides

Lanthanide contraction doesn’t only affect the lanthanides (from atomic number 57 to 71), but also the elements after.

For example:

Let’s compare the atomic radius and ionic radius of Zirconium and Hafnium. Zirconium (atomic number 40) lies prior to the lanthanides and Hafnium (atomic number 72) lies just after the lanthanides.

Atomic Radius of Zirconium is 159 pm & Hafnium is 156 pm
Ionic Radius of Zr4+ is 79 pm & Hf4+ is 78 pm

You can see the decrease in the atomic as well as the ionic radii of these two pre and post lanthanides.

✅Recommended read: Elements of the Periodic Table with Symbols and Atomic Numbers [PDF]

Final Words

So, that’s it and I hope this explains everything.

Lanthanide Contraction is considered to be one of the most interesting topics and also very important for Chemistry students.

Sometimes, a few questions related to this contraction is also asked in the IITJEE entrance and CBSE class 12th exams.

If you have any related query or doubts then let me know in the comments right now.

Also, share this article with the people who you think might be interested in reading it.

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  1. Some times its a pain in the ass to read what people wrote but this site is really user friendly! .

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