Alkali metals oxide are obtained by combustion of the metals.Although Na normally gives `Na_2O_2`,it will take up further oxygen at elevated pressure and temperature to form `NaO_2`.The per and superoxides of the heavier alkalies can also be prepared by passing stoichiometric amounts of oxygen into their solution in liquid ammonia.
The different alkali metal oxides can be distinguished by reaction with water.The superoxides reacts with `CO_2` and give oxygen gas.The stability of per and superoxides is based upon that larger cation can stablise larger anion, due to larger lattice energy.
Alkali metals dissolve in liquid ammonia.Dilute solutions are dark blue in colour but as the concentration increases above 3M, the colour changes to copper bronze and the solution acquires the metallic lusture due to the formation of metal ions clusters.The solutions of alkali metals in liquid ammonia are good conductors of electricity due to the presence of ammoniated cations and ammoniated electrons.However, the conductivity decreases as the concentrations increases, since ammoniated electrons and ammoniated cation associate.
On dissolving smaller (less than 3M) amount of sodium metal in
liquid ammonia at low temperature , which one of the following
does not occur ?

Options

A. Blue coloured solution is obtained
B. Ammoniated `Na^+` ion are formed in the solution
C. Liquid `NH_3` becomes good conductor of electricity
D. Liquid ammonia remains diamagnetic

Explanation

To solve the question regarding the behavior of sodium metal in liquid ammonia at low concentrations, we will analyze each statement provided in the context of the properties of alkali metals and their solutions in ammonia.

### Step-by-Step Solution:

1. **Understanding the Context**:
- Alkali metals, such as sodium (Na), react with liquid ammonia to form solutions that exhibit specific properties based on concentration.
- At low concentrations (less than 3M), the solution is dark blue due to the presence of ammoniated electrons.

2. **Analyzing Each Statement**:
- **Statement 1**: "Blue color solution is obtained."
- **Analysis**: True. At concentrations less than 3M, the solution is indeed dark blue.

- **Statement 2**: "Ammoniated Na⁺ ions are formed in the solution."
- **Analysis**: True. Sodium metal dissolves in ammonia to form ammoniated sodium ions (Na⁺).

- **Statement 3**: "Liquid ammonia becomes a good conductor."
- **Analysis**: True. The presence of ammoniated cations and electrons makes the solution a good conductor of electricity.

- **Statement 4**: "Liquid ammonia remains diamagnetic."
- **Analysis**: False. The solution at low concentrations is paramagnetic due to the presence of unpaired electrons from the ammoniated electrons. It only becomes diamagnetic when the concentration exceeds 3M, leading to the formation of electron clusters.

3. **Conclusion**:
- The statement that does not occur when dissolving a smaller amount of sodium metal in liquid ammonia at low temperature is that "liquid ammonia remains diamagnetic."

### Final Answer:
The correct answer is that **liquid ammonia remains diamagnetic** does not occur.

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