When NH4SCN is added to a solution of Fe3+ ions, the solution changes from yellow to orange. What is the best explanation for this color change?

The iron present in the solution is reduced because of the presence of SCN⁻ ions in solution

Explanation:

The clue in this problem is the color of the solution:

A solution of Fe³⁻ is yellow but when the Fe³⁺ is reduced by an oxidant to Fe²⁺ the solution change to orange color.

The SCN⁻ ion is a reducing agent than, in presence of a substance that can be reducted as Fe³⁺ ion will promote the reaction. That means the best explanation is:

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