Question

what happens when AgNO3 is left in atmosphere

Answer 1

Dear User,
Silver nitrate is sensitive to light. On exposure to atmosphere, it reacts with the atmospheric energy from the sun and decomposes to silver oxide and turns black in colour.
${\mathrm{AgNO}}_3\left(\mathrm{aq}\right)\stackrel{\mathrm{sunlight}}{\to }\mathrm{AgO}\left(\mathrm{s}\right)+{\mathrm{HNO}}_3\left(\mathrm{aq}\right)$