Consider the alkaline earth metals Be , Mg , Ca , Sr , and Ba . The number of metals that impart a characteristic colour to the Bunsen flame AND have a standard reduction potential E^ ( M ²⁺/ M ) more negative than -2.85 V is

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The alkaline earth metals that impart a characteristic colour to the Bunsen flame are Ca (brick red), Sr (crimson), and Ba (apple green). Be and Mg do not impart any colour due to their high ionization enthalpies. The standard reduction potentials E^ ( M ²⁺/ M ) for these metals are approximately: Be : -1.97 V Mg : -2.36 V Ca : -2.84 V Sr : -2.89 V Ba : -2.90 V The metals with an E^ value more negative than -2.85 V are Sr and Ba . Both Sr and Ba satisfy both conditions (imparting flame colour and having E^ Thus, th