Stability of beryllium carbonate Beryllium carbonate is reported to be unstable under normal conditions and should only be kept in a atmosphere of $\ce{CO2}$. Why and how this stability is maintained? Why does this compound decompose when kept in an atmosphere of oxygen?
Why and how is this stability maintained?


Beryllium carbonate decomposes into Beryllium oxide and Carbon dioxide.
$$\ce{BeCO3 &lt;=&gt; BeO + CO2}$$

According to Le Chatelier's principle one simply has to store it under a $\ce{CO2}$ atmosphere to push the equilibrium to the left.
$$\ce{BeCO3 &lt;&lt;=&gt; BeO + CO2}~\text{in excess}$$


  Why this compound decomposes when kept in atmosphere of oxygen?


When there is no $\ce{CO2}$ atmosphere the equilibrium is pushed to the right, which would be the "normal" case under standard conditions.
$$\ce{BeCO3 &lt;=&gt;&gt; BeO + CO2}$$