What is the rule for finding out how many valence electrons elements in groups 13-18 have

Are the earth's ocean floor and continents the same age geologically? why or why not?

What mistake did john needham make that caused him to conclude that spontaneous generation for microorganisms occurred? a. he re-contaminated his boiled broth solutions. b. he destroyed the vital force in the solutions. c. he did not boil his broth solutions, only warmed them. d. he failed to seal his flasks of boiled broth. e. he allowed his assistant to conduct the experiment which he did not monitor closely.

Polar zones are cold and tend to be dry because of a pressure system of cold. low high