The answer is b) 12 i believe
A phase change is when matter changes to from one state ( solid, liquid, gas, plasma) to another.
The element is Sr (strontium)
strontium is in atomic number 38 in the periodic table. Strontium has 2.8.8.8.8.2
it loses two electrons to become stable hence it has a charge of 2+. when strontium loses two electron it form ion with 36 electrons
