How are isotopes of the same element alike? different?

Isotopes are elements with the same number of protons but different number of neutrons

Yes you are correct use the scientific method

☆ionisation energy increases across a period from na -> ar☆ionisation energy decreases down a group from li -> fr☆ionic radius decreases across a period from na -> cl☆ionic radius increases down a groupfrom f -> ii hope it clarifies your doubts