A transition element containing only one electron in $4 \mathrm{s}$ orbital is

A transition element containing only one electron in $4 \mathrm{s}$ orbital is
  1. ${ }_{21} \mathrm{Sc}$
  2. ${ }_{23} \mathrm{Mn}$
  3. ${ }_{26} \mathrm{Fe}$
  4. ${ }_{29} \mathrm{Cu}$

Solution

The electronic configuration of $\mathrm{Cu}$ is
$(3 \mathrm{d})^{10}(4 \mathrm{s})^{1}$ ~

Asked in: JEE-TOPICTESTS-CHEMISTRY

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