Question

what is lanthanoid contractions

Answer 1

Helllo

Lanthanoid Contraction: The steady decrease in the atomic and ionic radii of the transition metals as the atomic number increases. This is because of filling of 4f orbitals before the 5d orbitals.
This contraction is size is quite regular. This is called lanthanoid contraction. it is due to lanthanoid contraction that the atomic radii of the second row of transition elements are almost similar to those of the third row of transition elements

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Answer 2

Answer:

• As we move along the lanthanoid series, the atomic number increases gradually by one.
• This means that the number of electrons and protons present in an atom also increases by one.
• As electrons are being added to the same shell, the effective nuclear charge increases.

• This happens because the increase in nuclear attraction due to the addition of proton is more pronounced than the increase in the interelectronic repulsions due to the addition of electron.
• Also, with the increase in atomic number, the number of electrons in the 4f orbital also increases.
• The 4f electrons have poor shielding effect. Therefore, the effective nuclear charge experienced by the outer electrons increases.
• Consequently, the attraction of the nucleus for the outermost electrons increases.
• This results in a steady decrease in the size of lanthanoids with the increase in the atomic number.
• This is termed as lanthanoid contraction.