Why lanthanoids and actinoids are called f-block elements?

P block elements

P block elements

D and f block elements

In case of d-block elements

D and F block elements

(i)with reference to structural variability and chemical reactivity write the differences between lanthanoids and actinoids (ii) Name a member of the lanthanoid series which is well known to exhibit +4 oxidation state

Number of s-block elements are:

On the basis of lanthanoid contraction, explain the following: (i) Nature of bonding in La_(2)O_(3) and Lu_(2)O_(3) . (ii) Trends in the stability of oxo salts of lanthanoids from La to Lu. (iii) Stability of the complexes of lanthanoids. (iv) Radii of 4d and 5d block elements. (v) Trends in acidic character of lanthanoids oxides.

State the common characteristic of lanthanoids and actanoids which places them in the f-block of elements.