3.3 f-Block Elements

  Periodic Table

• The elements of the periodic table in which the last electron gets filled up in the d orbital are called $d$-block elements.
• The $f$-block elements are from atomic number 58 to 71 and from 90 to 103.
• The lanthanides occur in nature in low abundance and therefore, these are called as rare earth elements.
• There are 28 $f$-block elements in the periodic table.
• The elements from atomic number 58 to 71 are called lanthanides because they come after lanthanides (57). The elements from atomic number 90 to 103 are called actinides because they come after actinium(89).
• All the actinide elements are radioactive.
• All the elements after atomic number 92 (i.e. U92) are transuranic elements.
• The general formula of these elements is $\left( {n - 2} \right){s^2}{p^6}{d^{10}}{f^{(1 - 14)}}\left( {n - 1} \right){s^2}{p^6}{d^{0 - 1}}n{s^2}$ where $n$=6 & 7.