6 s ▁sub sh ells . ▁As ▁such ▁configuration ▁strongly ▁res ists ▁removal ▁of ▁an ▁electron , ▁mer cur y ▁behav es ▁similarly ▁to ▁noble ▁gas ▁elements , ▁which ▁form ▁weak ▁b onds ▁and ▁thus ▁easily ▁mel ting ▁sol ids . ▁The ▁stability ▁of ▁the ▁ 6 s ▁shell ▁is ▁due ▁to ▁the ▁presence ▁of ▁a ▁filled ▁ 4 f ▁shell . ▁An ▁f ▁shell ▁poor ly ▁screens ▁the ▁nuclear ▁charge ▁that ▁increases ▁the ▁attract ive ▁C oul omb ▁interaction ▁of ▁the ▁ 6 s ▁shell ▁and ▁the ▁nucle us ▁( see ▁l anth an ide ▁contra ction ). ▁The ▁absence ▁of ▁a ▁filled ▁inner ▁f ▁shell ▁is ▁the ▁reason ▁for ▁the ▁somewhat ▁higher ▁mel ting ▁temperature ▁of ▁cad m ium ▁and ▁z inc , ▁although ▁both ▁these ▁met als ▁still ▁m elt ▁easily ▁and , ▁in ▁addition , ▁have ▁unus ually ▁low ▁bo iling ▁points . ▁Gold ▁has ▁atoms ▁with ▁one ▁less ▁ 6 s ▁electron ▁than ▁mer cur y . ▁Those ▁electrons ▁are ▁more ▁easily ▁removed ▁and ▁are ▁shared ▁between ▁the ▁gold ▁atoms ▁forming ▁relatively ▁strong ▁met all ic ▁b onds . ▁ ▁Z inc , ▁cad m ium ▁and ▁mer cur y ▁form ▁a ▁large ▁range ▁of ▁allo ys . ▁Among ▁the ▁z inc ▁containing ▁ones , ▁br ass ▁is ▁an ▁al loy ▁of ▁z inc ▁and ▁co pper . ▁Other ▁met als ▁long ▁known ▁to ▁form ▁binary ▁allo ys ▁with ▁z inc ▁are ▁al umin ium , ▁ant im ony , ▁b ism uth , ▁gold , ▁iron ,