(a)Using the ionic radii data calculate the coulombic force of attraction between the Mg2+ -O2- ion pair. (b) What is the repulsive force in this case? Calculate the minimum radius ratio for a coordination number of (a)4 and (b)6.
coulombic force = k Q1 Q2/ r2
putting values k = 9*10-9 N m2 C-2 , Q1 = +2 (1.6 *10-19) C , Q2 = -( 2 * 1.6 *10-19 ) C
radius r = radius ( Mg2+ ) + radius (O2-) = 0.65 * 10-10 + 1.40 * 10-10 = 2.05 * 10-10 m
= (9*10-9 N m2 C-2) (3.2 *10-19) C ( 3.2 *10-19 ) C / (2.05 * 10-10 )2 m
= 21.93 * 10-7 N m1
b) repulsive force is equal to force of attraction with negative sign = - 21.93 * 10-7 N m1
2) minimum radius ratio
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