Hydrogen most flammable gas
Hydrogen, as the first element on the periodic table, has an atomic number of 1. It is highly flammable and is the most common element found in our universe.
At room temperature mercury is the only metal that is in liquid form.
Metals such as sodium, potassium, rubidium, caesium and francium, which are alkali, are also reactive. Putting them in water can result in an explosion.
They are stored in oil to prevent this from happening.
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