Simplify the following text for a Grade 9 native English-speaking person.
Original: Nickel nitrate is the chemical compound Ni ( NO3 ) 2 or any hydrate thereof . The anhydrous form is not commonly encountered , thus `` nickel nitrate '' usually refers to nickel ( II ) nitrate hexahydrate .
Simplified: Nickel ( II ) nitrate , also known as nickelous nitrate , is a chemical compound .