Why do atoms join to form bonds?

Given the table below, what is the chemical formula for a compound between rb and the nitrate ion no3 -1? nitrate ion no3 -1 phosphate po4 -3 sulfate so4 -2 acetate c2h3o2 -1 ammonium nh4 +1 chromate cro4 -2 carbonate co3 -2 dichromate cr2o7 -2 permanganate mno4 -1 sulfite so3 -2 rbno3 rb2no3 rb(no3)2 rb2(no3)3

What is the empirical formula for c4h8o2

Which class of molecules functions as chemical signals? hormones water carbohydrates proteins