2.62 Predict the chemical formulas of the compounds formed by the following pairs of ions: (a) Cr3 and Br-, (b) Fe3 and O2-, (c) Hg2 2 and CO3 2-, (d) Ca2 and ClO3 -, (e) NH4 and PO4 3-.

it should be p1 v1 = p2 v2

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."

um i think it might be a car?