Question

Why are f-block elements called "Inner-transition elements" ?

Answer 1

The f block elements, numbers 57 to 70 and 89 to 102, are called the inner transition elements because of their placement in the periodic table due to their electron configurations.

Answer 2

Answer:

• The "F-block elements" are called as the “inner-transition elements” because of their unique electronic configuration.
• The valence electrons of these elements transitions into the (n-2) f block which is the "anti-penultimate energy level" and lies in the f-orbital. Hence these are called as 'inner transition elements'.
• They are represented by two series of elements – the lanthanoids and the actinoids in periods 6 and 7 of the periodic table.
• The valence electrons of the lanthonoids (14 elements like cerium, thorium etc) gradually transition into the 4f subshell.
• The valence electrons of the actinoids (14 elements like uranium, plutonium etc) gradually transition into the 5f subshell.