Definition of distance in physics

If element x has 99 protons how many electrons does it have

Aprisoner is forced to go into one of three rooms, but he can choose which room. the first room is ablaze with fire. the second one is rigged with explosives that will go off as soon as he enters. the third contains a pair of lions who haven't eaten in years. which room should he choose to survive?

The first law of thermodynamics states that heat added to a system is neither created nor destroyed but is as it changes into other forms of energy.