Using valence bond theory, show that `[Ni(CN)_4]^(2-)` complex is diamagnetic in nature. [Atomic number of Ni is 28].

Find the secondary valency of Ni in [Ni(CO)_4] .

Explain why the valency of magnesium with atomic number 12 is 2 and that of sulphur with atomic number 16 is also 2?

Using concept of slopes, show that the points (-2, 4), (1, 1) and (3, -1) are collinear.

Explain the following:- Ferri cyanide complex [Fe(CN)_6]^(3-) is weakly paramagnetic whereas Ferrocyanide complex [Fe(CN)_6]^(4-) is diamagnetic.

Show that the relation R defined in the set A of all polygons are as R = {(P_1,P_2) : P_1, P_2 in A} P_1 and P_2 have same number of sides is an equivalence relation. What is the set of elements in A which are related to the rectangle having sides 4 and 5 cm?

Two parallel Co-axial Coils of equal radius R and- numbers of turn N carrying equal currents I in same direction.are separated by a distance | R. Show that the magnetic field intensity B on the axis around the mid point between the coils is uniform over a very small distance as compared to R and is given by- B = (4/5)^(3/2) (mu_0IN)/R