Comparison of properties and crystalline structures of nitrates, sulphates and phosphates of Co(II) and Ni(II)

Abstract

The main objective of this project is to compare crystalline properties and structures of nitrates, sulphates and phosphates of Co(II) and Ni(II). Cobalt (Z = 27) and nickel (Z = 28) are transition metals. They present a valence shell with multiple electrons, cobalt is a d7 and nickel is a d8 , so they have the ability to give or receive electrons. Moreover, they can also change their oxidation state, being +2 the most common one, but they can also appear in the neutral form (0), +1 and +3. In few compounds, cobalt can present an oxidation state of +4. When studying the different structures, it is important to remark that they can form multiple polymorphs and appear in different symmetries, so there are plenty of possibilities. For example, phosphates are divided in diphosphates [M2P2O7] and orthophosphates [M3P2O8]. The studied structures are: trigonal Co(NO3)2, trigonal Ni(NO3)2 and cubic Ni(NO3)2; both α and β-CoSO4 and β-NiSO4; both monoclinic α and β-Co2P2O7 and both monoclinic α and β-Ni2P2O7; stable Co3P2O8 and metastable Co3P2O8 and Ni3P2O8. Each structure has particular properties, so the main objective of this paper is to determine which are the most common ones and see how they vary when changing the main ion (Co and Ni) and changing their crystalline structures.