I know the Elephant's Toothpaste experiment is an endothermic reaction, but what type of thermodynamic process is it, out of isobaric, isochoric, isothermal, or adiabatic?

The correct option is adiabatic

Explanation:

First of all, the Elephant's toothpaste experiment is an exothermic reaction as it requires the release of hot foam (heat).

The elephant's toothpaste experiment involves the addition of hydrogen peroxide to washing soap/liquid soap. Another solution of potassium iodide or dry yeast plus warm water is mixed and then added to the initial solution in a bottle to release the "hot foam". This release of heat as hot foam to the surrounding makes the process an adiabatic process.

Adiabatic process is a process in which there is no heat transfer between a system and it's surrounding except when transferred to it's surrounding as work

the atomic number will stay the same no matter how many electrons it has, so it doesn’t decrease nor increase. it’ll only change with a different number of protons