An example of a substance that is acidic is

Vinegar

Milk

Water

Bleach

Engineers have contribute to society in many ways like making the technology we use today or any type of power energy material

☆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