Kemija - 2019. ljeto, 3.

${\mathrm{L}\mathrm{i}}^{+},{\mathrm{N}\mathrm{a}}^{+},{\mathrm{K}}^{+}\backslash mathrm\{Li\}^\{+\},\; \backslash mathrm\{Na\}^\{+\},\; \backslash mathrm\{K\}^\{+\}$

${\mathrm{C}\mathrm{l}}^{-},{\mathrm{B}\mathrm{r}}^{-},{\mathrm{I}}^{-}\backslash mathrm\{Cl\}^\{-\},\; \backslash mathrm\{Br\}^\{-\},\; \backslash mathrm\{I\}^\{-\}$

${\mathrm{O}}^{2-},{\mathrm{F}}^{-},\mathrm{N}\mathrm{e}\backslash mathrm\{O\}^\{2-\},\; \backslash mathrm\{F\}^\{-\},\; \backslash mathrm\{Ne\}$

${\mathrm{K}}^{+},{\mathrm{C}\mathrm{a}}^{2+},\mathrm{K}\mathrm{r}\backslash mathrm\{K\}^\{+\},\; \backslash mathrm\{Ca\}^\{2+\},\; \backslash mathrm\{Kr\}$