Name a metal which combines with hydrogen gas. Name the compound formed.

The metal that combines with hydrogen gas is Sodium (Na). When Sodium combines with Hydrogen gas, the compound formed is Sodium Hydride (NaH).

Here are the steps of how this reaction occurs:

1. Sodium (Na), a highly reactive metal, comes into contact with Hydrogen gas (H2), a diatomic molecule.

2. A reaction occurs where Sodium donates one electron to Hydrogen, forming a positive Sodium ion (Na+) and a negative Hydrogen ion (H-).

3. These ions attract each other due to their opposite charges and form an ionic bond, creating the compound Sodium Hydride (NaH).

So, the chemical reaction can be written as:

2Na + H2 → 2NaH

This means that two moles of Sodium react with one mole of Hydrogen gas to form two moles of Sodium Hydride.