Question

Which of the following exhibit only +3 oxidation state ?

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> AIPMT 2012 (MAINS)

• A. $U$
• B. $Th$
• C. $Pa$
• D. $Ac$

Answer 1

The correct option is D $Ac$

$Th$ having atomic number 90 showing electronic configuration $\left[Rn\right]6d^{2}7s^2$ showing 2 oxidation states of +3 and +4.
$Ac$; atomic number 89 showing electronic configuration $\left[Rn\right]6d^{2}7s^1$ it shows stable oxidation state of +3 only.
$Pa$; atomic number 91; showing electronic configuration $\left[Rn\right]5f^{2}6d^{1}7s^2$ showing oxidation states of +3, +4 and +5.
$U$ mainly used in nuclear reactions having atomic number 92 and showing electronic configuration as $\left[Rn\right]5f^{3}6d^{1}7s^2$ showing 4 oxidation states +3, +4, +5 and +6.
Option (c) is correct