chlorate ion CIO3(aq) CIO2(g) +257 hypochlorite ion Clo(ag +42 CiF(g) 218 oxide(di-) C120(g) 266 perchlorate ion CIO(aq) bifluoride CIF3(g +282 123 Chromium Cr(s) 175 352 139 Cr(aq) 256 205 (l) chloride CrCl2(s) +115 356 (ln) chloride CrCl3(s) +123 chromate ion CrO4(aq) 881 dichromate ion Cr2O7(aq) -1490 +262 1301 (Ill)oxide Cr2O3(s) -1140 -1058 (VI)oxide CrO3(s) -513 (lll) sulfate Cr2(SO4)3(s) 2911 Cobalt Co(s) Co(g) +380 Co(aq) -113 (n carbonate CoCO3 (s) 713 637 (n chloride CoCl(s) -313 (n chloride COCl2·6H2O(s) 2115 -1725 (n hydroxide Co(OH)2(s)(pink) CoO(s) (n) sulfate CoSO4(s) +118 (I sulfate heptahydrate CoSO·7H2O(s) Cu(g) Cu(aq) +6289 Cl− (aq) −167 +57 −131 chlorate ion ClO3 − (aq) −104 +162 −8 dioxide ClO2(g) +102 +257 +120 hypochlorite ion ClO− (aq) −107 +42 −37 monofluoride CIF(g) −54 +218 −56 oxide (di-) C12O(g) +80 +266 +98 perchlorate ion ClO4 − (aq) −128 +184 −8 trifluoride ClF3(g) −163 +282 −123 Chromium Cr(s) 0 +24 0 Cr(g) +397 +175 +352 Cr2+ (aq) −139 −165 Cr3+ (aq) −256 −205 (II) chloride CrC12(s) −395 +115 −356 (III) chloride CrCl3(s) −556 +123 −486 chromate ion CrO4 − (aq) −881 +50 −728 dichromate ion Cr2O7 2− (aq) −1490 +262 −1301 (III) oxide Cr2O3(s) −1140 +81 −1058 (VI) oxide CrO3(s) −580 +72 −513 (III) sulfate Cr2(SO4)3(s) −2911 +259 −2578 Cobalt Co(s) 0 +30 0 Co(g) +425 +180 +380 Co2+(aq) −58 −113 −54 Co3+(aq) +92 −305 +134 (II) carbonate CoCO3(s) −713 +89 −637 (II) chloride CoCl2(s) −313 +109 −270 (II) chloride hexahydrate COC12·6H2O(s) −2115 +343 −1725 (II) hydroxide Co(OH)2(s) (pink) −540 +79 −454 (II) oxide CoO(s) −238 +53 −214 (II) sulfate CoSO4(s) −888 +118 −782 (II) sulfate heptahydrate CoSO4·7H2O(s) −2980 +406 −2474 Copper Cu (s) 0 +33 0 Cu(g) +337 +166 +298 Cu+ (aq) +72 +41 +50 Cu2+(aq) +65 −98 +65