The chemical formula for ferric nitrate/ iron nitrate is Fe(NO3)3.
HgCl is the empirical formula of mercury I (mercurous) chloride, for which the full chemical formula is Hg2Cl2
Formula: Hg2(OH)2
Th mercurous ion is a diatomic catiion, Hg22+, consisting of two mercury atoms covalently bonded together.
The chemical formula for anhydrous magnesium nitrate is Mg(NO3)2.
Hg2S is mercurous sulfide.
Hg3PO4 is the chemical formula for mercurous phosphate.
Hg22+ + NO3- -----> Hg2(NO3)2
Hg2F2
Hg2CO3
The chemical formula of a nitrate is MeNO3 (Me is the metal).
The chemical formula for ferric nitrate/ iron nitrate is Fe(NO3)3.
HgCl is the empirical formula of mercury I (mercurous) chloride, for which the full chemical formula is Hg2Cl2
Formula: Hg2(OH)2
Essentially ALL the metallic nitrates are soluble, even mercurous nitrate, perhaps the only mercurous salt that is soluble.
Mercurous nitrate or mercury (I) nitrate, assuming that the formula given was the best approximation available to the questioner for Hg2(NO3)2.
The chemical name is nitrate and the chemical formula is (NO3)-.