Liquids boil when: A. Vapor pressure is very high
B. Vapor pressure is equal to atmospheric pressure
C. Vapor pressure is greater than the atmospheric pressure
D. Vapor pressure is lower than atmospheric pressure

They are like other investigations? say there was a murder u have to do blood test and finger prints which run through a lab. 

☆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