`""_(57)La` and `""_(71)Lu` Lu have no partially filled 4f-subshell, yet these are included in lanthanoids. Explain.

The transition elements are those elements which have partially filled penultimate d-subshells in their elementary form or in their commonly occurring oxidation states.

The +3 ion of which one of the following has half filled 4f subshell?

The elements in which electrons are progressively filled in 4f-orbitals are calleD: (A)Actinoids (B)Transition elements (C)Lanthanoids (D)halogens.

We have a vessel in shape of a cuboid partially filled with water. It base is square wilth an area of 4.5dm^(2) (1dm=10cm) and a vessel contains water up to 2 cm height. Then we place wooden cube inside water. The wood has mass 4kg and specific gavity 0.5 . The base of the wooden cube is horizontal. Find the height of water level above the base of the wooden block.

The IUPAC definition of a transition element is that it is an element that has an incomplete d-subshell in either the neutral atom or its ion. Thus the group 12 elements are member of the d-block but are not transition elements. Chemically solft members of the d-block occurs as sulphide minerals and are partially oxidised to obtain the metal, the more electropositive 'hard' metals occurs as oxides and are extracted by reduction. Opposite to p-block elements, the higher oxidation states are favoured by the heavier elements of d-block Metals on the right of the d-block tend to exist in low oxidation states and form complexes with the ligands. Square-planar complexes are common for the platinum metals and gold in oxidation states that yield d^8 electronic configuration, which include RH(I),Ir(I),Pd(II),Pt(II) and Au(III). The most distinctive features/properties of transition metal complex is their wide range of colours.The crystal field theory attributes the colour of the coordination compounds to d-d transition of the electron.It is important to note that (a) in absence of ligand, crystal field spilling does not occur and hence the substances is colourless, (b) the type of ligand also influences the colour of the complexes. Which of the following has dsp^2 hybridisation and is diamagnetic in nature ? (i) Na_4[Cr(CO)_4] , (ii) [Ni(DMGH)_2] , (iii) [PtHBr(PEt_3)_2] (iv) [As(SCN)_4]^(3-) , (v) [AuBr_4]^(-)

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.

A: Lanthanoids have +3 as most common oxidation state. R: Electrons of 4f in lanthanoids rarely participate