Characteristics of Actinides

  • Electronic Configuration

Electronic configuration of lanthanum and Actinides are given below –

Ac(89)              Actinium                                     [Rn] 6d17s2

Th(90)              Thorium                                       [Rn] 6d27s2

Pr(91)              Proactinium                                  [Rn] 5f26d16s2    

U(92)                 Uranium                                     [Rn] 5f36d16s2

Np(93)            Neptunium                                     [Rn] 5f46d16s2

Pu(94)             Plutonium                                      [Rn] 5f67s2

Am(95)             Americium                                   [Rn] 5f7 7s2

Cm(96)            Curium                                           [Rn] 5f76d17s2

Bk(97)               Berkelium                                    [Rn] 5f97s2

Cf(98)              Californium                                   [Rn] 5f107s2

Es(99)               Einsteinium                                  [Rn] 5f117s2

Fm(100)            Fermium                                      [Rn] 5f127s2

Md(101)           Mendelevium                                [Rn] 5f137s2

No(102)              Nobelium                                    [Rn] 5f147s2

Lr(103)              Lawrencium                                 [Rn] 5f146d17s2

Oxidation state

The most common and the stable oxidation state of Actinides is +3 due to the very small  energy difference between 5f, 6d and 7s subshells; it is very easy to excite the  electrons to the higer energy levels. Some elements of this series exhibits +4 oxidation state e.g. – Th and Pu, some exhibits +5 oxidation state e.g.- Pa and Np, and uranium exhibits +6 oxidation state. This uneven distribution of oxidation state in actinides from +2 to +7 is due to the poor shielding effect of 5f electrons.

  • Am (Americium)- atomic number 95, electronic configuration is [Rn] 5f7 7s2 and No (Nobelium) atomic number 102, electronic configuration is [Rn] 5f147s2.
  • They exhibit 2+ oxidation state  by acquiring half filled and fully filled electronic configuration, f7 and f14.
  •  Thorium (Th) exhibit +4 oxidation state by acquiring noble gas configuration.
  • Proactinium shows +4 and +5 oxidation state but its most stable oxidation state is +5 in solution. It rapidally hydrolyses when it combines with hydroxide ion, and form soluble or insoluble hydroxy-oxide solids. These solids stick to the surface of the vessel in which they are contained. Proactinium has linear structure in solid and solution form.
  • Uranium exists in +3, +4, +5 and +6 oxidation state in aqueous solution. Its most stable oxidation state is +6 because after losing six electrons, it acquires f0 configuration.
  • Np and Pu exits in +7 oxidation state.
  • Color of actinides

Actinides form colored compounds due to partially filled f orbital resulting f-f transition. The actinides with f0 and f7 electrons are colorless. The color of the compounds is depends on the number of unpaired electrons present in 5f-orbital.

  • Melting and Boiling point

The melting and boiling point of actinides is very high like lathanides but the trend is not regular with increasing atomic number along the series of actinides.

  • Complex formation

They have higher tendency to form complexes than the lanthanides because of following reasons –

  • Small size
  • Number of unpaired electron in 5f orbital
  • High effective nuclear charge

  • Density

All elements of the actinides series have higher density except thorium and americium.

  • Ionisation energy

The ionization energies of the actinides are lower than the lanthanides.This is because the electrons of 5f orbital are more effectively shielded  from nuclear charge than 4f.

  • Magnetic properties

All elements of the actinides series are paramagnetic in nature due to presence of unpaired electrons.

  • Electropositive character

All elements in the actinide series are highly electropositive .

Related Posts

  • 87
    Actinides are those elements in which 5f subshell is gradually filled from actinium to lawrencium. The Actinides series contains consecutive 14 elements from atomic number 89 to 103, from actinium to lawrencium, called Actinides.They are called Actinides because they start immediately after acitinium, the first elements of this series.They are…
    Tags: elements, actinides, series, number, f-block, inorganic, chemistry, introduction
  • 82
    The f –block elements are those in which atoms or ions have valence electrons  in f-orbital. They are also called inner transition elements because the last or valence electron enters in (n-2)f orbital means in anti-penultimate energy level. They are also referred as rare earth elements. The general electronic configuration…
    Tags: elements, f-block, actinides, series, configuration, electronic, inorganic, chemistry, introduction
  • 79
    Atomic and ionic size – As the atomic number increases, the atomic size increases and  effective nuclear charge also increases which attracts the outermost shell more effectively. So, as we move left to right means from actinium to lawrencium in the actinide series, there is gradual decrease in the the…
    Tags: number, actinides, f-block, elements, inorganic, chemistry, introduction
  • 76
    Actinides are strong reducing agent and very reactive in crushed from. They are radioactive due to less stable nuclei and also have no stable isotopes. They have variable oxidation state due to which its study is quite difficult – They readily react with HCl but when they react with nitric…
    Tags: actinides, oxidation, state, f-block, elements, inorganic, chemistry, introduction
  • 71
    In lanthanides series, first few elements are quite reactive with calcium but with increase in atomic number, their reactivity is quite similar to aluminum. Lanthanides when reacted with carbon in inert atmosphere, then there is the formation of carbides.On gentle heating, it combine with hydrogen. Lanthanides form halides in the…
    Tags: f-block, elements, inorganic, chemistry, introduction

Leave a Reply

Your email address will not be published. Required fields are marked *