Answer:
Endothermic
Exothermic
Endothermic
Exothermic
Exothermic
Exothermic
Explanation:
Endothermic is when a reaction absorbs heat.
Exothermic is when a reaction releases heat.
There are 2 valence electrons
2Na + H₂ = 2NaH (sodium-hydride).
Answer: They have too many protons in the nucleus.
Explanation: Noble gas. The noble gases are the chemical elements in group 18 of the periodic table. They are the most stable due to having the maximum number of valence electrons their outer shell can hold. Therefore, they rarely react with other elements since they are already stable.
