The main-group elements are the forty-four elements that occupy groups 1A-8A of the periodic table. Main-group elements are important because of their high natural abundance both in the Earth's crust and in the human body and are commercially valuable.

Ahypothesis is? close agreement by competent observers of observations of the same phenomena. a guess that has been tested over and over again and always found to be true. an educated guess that has yet to be proven by experiment. the long side of a right triangle. a synthesis of a large collection of information that includes guesses.

Complete the statement about memory improvement. ( )involves organizing and breaking down information into easier groups to expand capacity. rehearsal is the verbal repetition of information. these techniques are especially important for the improvement of ( ) memory.

Compare the horizontal displacement of the two balls as they travel to the ground. what do you observe?