Chemistry

Problem

Which of the following pairs of cations will turn borax beads blue in an oxidising flame? a.

\text{Fe}^{2+}

and

\text{Co}^{2+}

\text{Co}^{2+}

and

\text{Cu}^{2+}

\text{Cu}^{2+}

and

\text{Mn}^{2+}

\text{Cu}^{2+}

and

\text{Cr}^{3+}