The form of oxygen that combines three oxygen atoms to each molecule, is found in the stratosphere and shields out harmful uv rays from the sun is:

This form of the oxygen molecule is Ozone, O3.

They can measure  the amount of energy gained or lost

☆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