text: oxidation state? oxidation states for all atoms uo2 2+     u=               o= as2o3      as=              o= nabio3     na=              o=                 bi= as4           as= haso2      h=                  as=              o2= mg2p2o7  mg=               o=               p= na2s2o3 na=                 o=              s= hg2cl2     hg=                cl= ca(no3)2   ca=               o=               n= need help i am confuse uo2, o=-2, u=-4 ca(no3)2, ca=+2, o=-2, n=5