• # question_answer 1) In what ways lithium shows similarities to magnesium in its chemical behaviour?

Lithium resembles magnesium mainly due to the similarity in sizes of their atoms (Li = 152pm, Mg = 160 pm) and ions ($L{{i}^{+}}$ = 76 pm, $M{{g}^{2+}}$ = 72 pm). Both have nearly same electro negativity. Some of chemical similarities are: (i) Both $LiOH$ and $Mg{{(OH)}_{2}}$ are weak bases. These are decomposed on heating. $2LiOH\to L{{i}_{2}}O+{{H}_{2}}O$ $Mg{{(OH)}_{2}}\to MgO+{{H}_{2}}O$ (ii) Both form ionic nitrides which are decomposed by water. $6Li+{{N}_{2}}\to 2L{{i}_{3}}N$ $3Mg+{{N}_{2}}\to M{{g}_{3}}{{N}_{2}}$ $L{{i}_{3}}N+3{{H}_{2}}O\to 3LiOH+N{{H}_{3}}$ $M{{g}_{3}}{{N}_{2}}+6{{H}_{2}}O\to 3Mg{{(OH)}_{2}}+2N{{H}_{3}}$ (iii) Both combine with carbon on heating. The carbides yield acetylene on hydrolysis. $2Li+2C\to L{{i}_{2}}{{C}_{2}}$ $Mg+2C\to Mg{{C}_{2}}$ $L{{i}_{2}}{{C}_{2}}+2{{H}_{2}}O\to 2Li(OH)+{{C}_{2}}{{H}_{2}}$ $Mg{{C}_{2}}+2{{H}_{2}}O\to Mg{{(OH)}_{2}}+{{C}_{2}}{{H}_{2}}$ (iv) Carbonates of Li and Mg decompose on heating. $L{{i}_{2}}C{{O}_{3}}\to L{{i}_{2}}O+C{{O}_{2}}$ $MgC{{O}_{3}}\to MgO+C{{O}_{2}}$ (v)$LiF,L{{i}_{3}}P{{O}_{4}},L{{i}_{2}}{{C}_{2}}{{O}_{4}}$and$L{{i}_{2}}C{{O}_{3}}$like the corresponding salts of magnesium are insoluble in water. (vi) $LiCl$like$MgC{{l}_{2}}$ is deliquescent. Both arc soluble in alcohol and pyridine. Show covalent nature. (vii) The bicarbonates are not known in solid state but only known in solutions.