What is the primary valence of nickel in NiCl₂ · 6H₂O ?
In NiCl₂ · 6H₂O, formulated as [Ni(H₂O)6]Cl₂, the primary valence is the oxidation state of Ni, satisfied by 2 ionizable Cl^- ions, so it is 2. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Relevant Chemistry topic covering principles and examples as per NCERT.