If 20 grams of NaOH was dissolved in enough water to make 250 mL NaOH Solution, What is the Molarity?

It conforms what ever surface its in.

Ido not understand. 

☆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