\"moving down group 2a (alkaline earth metals), which element has the largest first ionization energy? \" is the answer to this: radium? . also, could you explain what a \"first\" ionization energy is? .

Ionization energy is the energy required to remove the outermost electron from one mole of gaseous atom to produce 1 mole of gaseous in to produce a charge of 1. The greater the ionization energy, the greater is the chance f the electron to be removed from the nucleus. In this casse, Radium has the largest ionization energy.

thats a little if u want the answer just look it up on google thats what i do haha : )

the temperature of the gas, in k, not celsius.