When making a guess and retesting this information a theory or may be formed which explains why something has occurred or what it may look like.

When making a guess and retesting this information a theory or hypothesis may be formed which explains why something has occurred or what it may look like. A hypothesis is a statement or fact that we wish to prove or disprove using scientific methods under certain controlled conditions. Hence the guess or assumption is authenticated with the valid reasoning of statistical theory.

The density would be 1.622

☆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