Answer:
4, 3, 2, 1
Explanation:
I'm not sure if this is correct but I know that to form helium you will need increase a high amount of temperature of hydrogen gas that cause the hydrogen to lose their electron. Due to the increasing tempture the hydrogen atoms are moving faster and collinding with one another. When they are colliding fast in that gas phase with high amont of heat, the hydrogen atoms will collide and form together to make helium.
This is the best way I could explain it.
