Alkali metals dissolve in liquid $NH_{3}$ then which of the following observation is not true?

Question

Accepted Answer

When alkali metals dissolve in liquid ammonia, several interesting phenomena occur due to the interaction between the metal atoms and the ammonia molecules. Let's explore why Option 3 is the correct answer and why the other options are incorrect.

1. **Option 3: It becomes diamagnetic.**  
   This statement is not true. When alkali metals dissolve in liquid ammonia, they form a solution containing solvated electrons. These solvated electrons are unpaired, which means the solution is actually paramagnetic, not diamagnetic. Paramagnetic substances have unpaired electrons and are attracted to magnetic fields, whereas diamagnetic substances have all paired electrons and are repelled by magnetic fields. Therefore, the solution cannot be diamagnetic, making Option 3 the correct answer as the observation that is not true.

2. **Option 1: It becomes bronze colour on concentration.**  
   This statement is true. As the concentration of the alkali metal in the ammonia solution increases, the color of the solution changes from blue to a bronze or golden color. This change is due to the increased concentration of solvated electrons, which alters the way light is absorbed and reflected by the solution.

3. **Option 2: Solution turns blue due to solvated electron.**  
   This statement is true. When alkali metals dissolve in liquid ammonia, they release electrons that become solvated by the ammonia molecules. These solvated electrons are responsible for the deep blue color of the dilute solution. The blue color is a characteristic feature of the presence of solvated electrons in the solution.

4. **Option 4: Solution becomes conducting.**  
   This statement is true. The presence of free, solvated electrons in the solution makes it highly conductive. These electrons can move freely through the solution, allowing it to conduct electricity effectively.

In summary, Option 3 is the correct answer because the solution formed by dissolving alkali metals in liquid ammonia is paramagnetic due to the presence of unpaired solvated electrons, not diamagnetic. The other options describe true observations related to the behavior of alkali metals in liquid ammonia.