一、依据溶液的颜色如果试题已指明溶液无色 ,则有色离子不能大量共存。常见呈现颜色的离子有 :外壳电子数为 9～ 1 7的第一过渡系元素的水合离子 ,能吸收一定波长的可见光 ,使其离子由基态跃迁到激发态 ,而呈现颜色。这些离子的颜色列于表 1。表 1　第一过渡系元素离子的颜色 First, based on the color of the solution If the test has been indicated that the solution is colorless, the colored ions can not coexist in large quantities. Common color rendering ions are: the number of shell electrons 9 to 17 of the first transition element hydrated ions, can absorb a certain wavelength of visible light, the ion transition from the ground state to the excited state, and the color. The colors of these ions are listed in Table 1. Table 1 first transitional elemental ion color