$(A)$ $\left[ Ni \left( H _{2} O \right)_{2}( en )_{2}\right]^{2+}$
$(B)$ $\left[ Ni \left( H _{2} O \right)_{4}(\text { en })\right]^{2+}$ અને
$(C)$ $\left[ Ni ( en )_{3}\right]^{2+}$
$(A)\,\,\,\,[Ni(H_2O)_5NH_3]^{2+},$
$(B)\,\,\,\,[Ni(H_2O)_4(NH_3)_2]^{2+}$
$(C)\,\,\,\,[Ni(H_2O)_3(NH_3)_3]^{2+}$
$(en =$ ઇથેન $-1, 2-$ ડાયએમાઇન$)$
[પરમાણુ ક્રમાંક : $Zn = 30, Sc = 21, $$Ti = 22, Cr = 24$]