Al, since it is the only metal in that list
Sodium Phosphide has a formula of Na3P . In order to bond ionically the charges must be equal and opposite. It will take one -3 phosphide ion to balance three +1 sodium ions forming a magnesium phosphide molecule of Na3P
Even though two grams seemed to disappear or vanish, the law of conversation of mass still holding true. Mercuric oxide, when heated, forms a gas of mercury and oxygen. During the investigation, some gas could have escaped or evaporated.
