Using the Kf value of 1.2x10^9 calculate the concentration of Ni^+2 (aq) and Ni(NH3)6^+2 that are present at equilibrium after dissolving 1.22g NiCl2 in 100.0 mL of NH3 (aq) solution such that the equilibrium concentration of NH3 is equal to 0.20 M

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6