Question

which is a gas at room temperature that reacts violently with other elements without heating.it is the most electro negative element

Answer 1

ammonium chloride and ammonia

Answer 2

The gas that is at room temperature reacts violently with other elements without heating is ammonium chloride ammonia, mercury or sodium.

Basically, the electronegative element will be adopting -1 oxidation state. Fluorine when blend with oxygen will be forming oxygen fluoride.

Basically, fluorine is considered as the most electro negative element. Its electro negativity would range around 3.98.