If you use its electronic structure the last number should be a five so something like (2,5), (2,8,5) or (2,8,8,5) etc.
The elements therefore with 5 as it's final number and 5 on the outer orbit are N, P, As, Sb, Bi, Uup. Therefore with the answers given to you the answer is most likely 4) Phosphorus. <span />
Potassium -40half life = 1.28 ×10∧9. Radioisotope can be used to determine the age of fossils, to treat skin disease, to sterilize foodstuffs, and also to sterilize surgical instruments. Radioisotope dating is a way to estimate a fossil's age by a method of analyzing the elemental isotopes which are within the rocks which it is in.
