Characteristics Of Lanthanides

  • Electronic Configuration

Electronic configuration of lanthanum and lanthanides are given below –

La(57)              Lanthanum                                  [Xe] 5d16s2

Ce(58)              Cerium                                        [Xe] 4f15d16s2

Pr(59)              Praseodymium                             [Xe] 4f36s2   

Nd(60)             Neodymium                                [Xe] 4f46s2

Pm (61)            Promethium                                 [Xe] 4f56s2

Sm(62)             Samarium                                    [Xe] 4f66s2

Eu(63)              Europium                                    [Xe] 4f76s2

Gd(64)             Gadolinium                                  [Xe] 4f75d16s2

Tb(65)               Terbium                                       [Xe] 4f96s2

Dy(66)              Dysprosium                                 [Xe] 4f106s2

Ho(67)               Holmium                                     [Xe] 4f116s2

Er(68)                Erbium                                        [Xe] 4f126s2

Tm(69)              Thulium                                        [Xe] 4f136s2

Yb(70)              Ytterbium                                     [Xe] 4f146s2

Lu(71)               Lutetium                                       [Xe] 4f14 5d1 6s2

  • Oxidation State –

The most common oxidation state of lanthanides is +3 which is obtained by removing two electrons from 6s and one electron from 4f. The +3 oxidation state of lanthanides is most stable due to the high energy difference between 4f and 6s; it is very difficult to remove more electrons from 4f-orbital. Some elements of this series exhibit +2 oxidation state e.g., – Sm, Eu, Tm, Yb, they have +2 oxidation state in aqueous solution,  and some of the elements exhibit +4 oxidation state e.g., – Pr, Ce, Tb, and Dy.

This uneven distribution of oxidation state of lanthanides is due to the extra stability of empty, half filled or fully filled f-subshell because the stability of f-orbital affects the oxidation state of lanthanides.

  • Eu (Europium) – atomic number 63, electronic configuration is [Xe]4f76s2 and Yb (Ytterbium) – atomic number 70, electronic configuration is [Xe]4f146s2.

They show +2 oxidation state by losing two electrons from 6s – subshell and attains extra stability by half-filled and fully- filled electronic configuration, 4f7 and 4f14 and readily converted into Eu+2 and Yb+2. Then, Eu+2 and Yb+2 changes into Eu+3 and Yb+3 which is the common oxidation state of lanthanides and acts as strong reducing agent.

  • Ce (cerium) – atomic number 58, electronic configuration is [Xe]4f15d16s2 and Tb – atomic number 65, electronic configuration is [Xe]4f96s2.

They show +4 oxidation states by acquiring extra stability by noble gas and half-filled electronic configuration, f0 and f7. But they revert to common oxidation state +3 and acts as strong oxidizing agents.

Colour of lanthanides

Lanthanides form colored compounds in their +3 oxidation state both in  solid  state as well as in solution form. Actually, the color of the compounds is depends on the number of unpaired electrons present in f-orbital. They have partially filled f-orbital resulting f-f transition is due to absorption in visible region. The lanthanides are in  other oxidation state (+2 ans +4) and iso electronic with their counterparts will not form colored compounds.

Magnetic properties –

All lanthanides are paramagnetic except – Lu+3, Yb+3, Ce+4 due to unpaired electrons in the f-orbital. Magnetic moment can be calculated by –

                                      μeff     =     (4S (S+1) + L(L+1))1/2

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