How many atoms are in the peroxide h2o2 molecule? explain.

There are two hydrogen and two oxygen molecules because the number next to the atomic number is how many there are.

There are 2 hydrogen atoms and 2 oxygen atoms in hydrogen peroxide molecule. Hence total number of atoms is 4.

☆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