Magnesium burns in air to give

Which of the following statements is incorrect?

The alkali metals form salt-like hydrides by direct synthesis at elevated temperatures. The thermal stability of these hydrides decreases in which of the following orders?

Write the general chemical reaction that shows the dissolution of an alkali metal in liquid ammonia.

Which of the following is thermally most stable?

Metal-ammonia solutions of group $1$ and group $2$ metals differ in