Why are horses and donkeys considered the same species even though they can produce offspring

Donkeys and horses can have a mule together, but the mule is unable to have offspring of its own. That is why horses and donkeys are considered to be different species - their offspring is infertile

idk what the options are but

these is a strong electrostatic attraction between the ions hence a lot of energy is needed to overcome this attraction

this is why the boiling points are so high

if someone had the list of traits you provided