Q120P - Chemistry: Molecular Nature Of Matter And Change

Question

In 1940, when the elements Np and Pu were prepared, a controversy arose about whether the elements from Ac on were analogs of the transition elements (and related to Y through Mo) or analogs of the lanthanides (and related to La through Nd). The arguments hinged primarily on comparing observed oxidation states to those of the earlier elements. 

(a) If the actinides were analogs of the transition elements, what would you predict about the maximum oxidation state for U? For Np? 

(b) If the actinides were analogs of the lanthanides, what would you predict about the maximum oxidation state for U? For Pu?

Step-by-Step Solution

Answer

(a) The maximum oxidation state of U and Np is 6+ and 7+, respectively, if the actinides were analogs of the transition elements.

(b) The maximum oxidation state of U and Pu is 3+ and 3+, respectively, if the actinides were analogs of the lanthanides elements.

Step 1: Given Information

The given information is to find the analogs of coordination compounds.

Step 1: Concept Introduction

A coordination complex consists of a central atom or ion, typically metallic and termed the coordination center, and a surrounding array of bound molecules or ions, which are successively called ligands or complexing agents.

Step 3: Oxidation states of U and Np

(a)

If and will follow the transition metals in the determination of the highest oxidation state, the formula in determining oxidation state applies to them.

For U,

number of unpaired electrons = 4

Thus, 

the highest oxidation state = 4+2 = 6+

For Np, 

number of unpaired electrons = 5

Thus,

the highest oxidation state = 5+2 = 7+

Step 4: Oxidation states of U and Pu

If U and Pu are analogs of lanthanides, then they will follow the oxidation state of most lanthanides. Lanthanides have an oxidation state of 3+, where they are most stable. Therefore, the highest oxidation state of U and Pu is 3+.