• # question_answer 69)   Lithium resembles magnesium in some of its properties. Mention properties and give reasons for this resemblance.

Lithium shows diagonal relationship with magnesium. The resemblance between the two elements is due to following reasons : (a) Atomic radius and ionic radius of both are nearly the same. (b) Electro negativities of both are quite comparable. (c) Both have high polarising power. Similar properties (i) Both combine with nitrogen on heating. $6Li+{{N}_{2}}\to 2L{{i}_{3}}N$ $3Mg+{{N}_{2}}\to M{{g}_{3}}{{N}_{2}}$ (ii) Both form only monoxide. $4Li+{{O}_{2}}\to 2L{{i}_{2}}O$ $2Mg+{{O}_{2}}\to 2MgO$ (iii) Carbonates of both decompose on heating.                 $L{{i}_{2}}C{{O}_{3}}\to L{{i}_{2}}O+C{{O}_{2}}$                 $MgC{{O}_{3}}\to MgO+C{{O}_{2}}$ (iv) $LiF,L{{i}_{3}}P{{O}_{4}},L{{i}_{2}}{{C}_{2}}{{O}_{4}}$and$L{{i}_{2}}C{{O}_{3}}$ like the corresponding compounds of magnesium are insoluble in water.