▁a que ous ▁solution , ▁and ▁un hex quad ium ( II ) ▁should ▁behave ▁more ▁similarly ▁to ▁lead ▁than ▁un hex quad ium ( IV ) ▁and ▁un hex quad ium ( VI ). ▁ ▁Un hex quad ium ▁should ▁be ▁a ▁soft ▁metal ▁like ▁mer cur y , ▁and ▁met all ic ▁un hex quad ium ▁should ▁have ▁a ▁high ▁mel ting ▁point ▁as ▁it ▁is ▁predicted ▁to ▁bond ▁c oval ently . ▁It ▁is ▁also ▁expected ▁to ▁be ▁a ▁soft ▁Lewis ▁acid ▁and ▁have ▁A hr lands ▁soft ness ▁parameter ▁close ▁to ▁ 4   e V . ▁It ▁should ▁also ▁have ▁some ▁similar ities ▁to ▁og an ess on ▁as ▁well ▁as ▁to ▁the ▁other ▁group ▁ 1 2 ▁elements . ▁Un hex quad ium ▁should ▁be ▁at ▁most ▁moder ately ▁re active , ▁having ▁a ▁first ▁ion ization ▁energy ▁that ▁should ▁be ▁around ▁ 6 8 5   k J / m ol , ▁compar able ▁to ▁that ▁of ▁mol y b den um . ▁Due ▁to ▁the ▁l anth an ide , ▁act in ide , ▁and ▁super act in ide ▁contra ctions , ▁un hex quad ium ▁should ▁have ▁a ▁met all ic ▁radius ▁of ▁only ▁ 1 5 8   pm , ▁very ▁close ▁to ▁that ▁of ▁the ▁much ▁l ighter ▁mag nes ium , ▁despite ▁its ▁being ▁expected ▁to ▁have ▁an ▁atomic ▁weight ▁of ▁around ▁ 4 7 4   u , ▁about ▁ 1 9 . 5   times ▁as ▁much ▁as ▁that