<p>Give reasons:</p>

<p>(a) Of the&nbsp;<span class="equation">\(d^4\)</span>&nbsp;species, <span class="equation">\(Cr^{2+}\)</span>is strongly reducing while <span class="equation">\(Mn^{3+}\)</span>is strongly oxidising.​​​​​​​​​​​​​​​​​​​​​</p>

<p>(b) The&nbsp;<span class="equation">\(d^1\)</span>&nbsp;configuration is very unstable in ions.​​​​​​​</p>