An atom of helium and one of argon are singly ionized - one electron is removed from each. The two ions are then accelerated from rest by the electric field between two plates with a potential difference of 150 V.

What happens after the two ions accelerate from one plate to the other?

a) The helium ion has more kinetic energy.
b ) The argon ion has more kinetic energy.
c) Both ions have the same kinetic energy.
d) There is not enough information to say which ion has more kinetic energy.