ASTRON 2B03 Lecture Notes - Lecture 4: Atomic Number, Chemical Element, Uucp

• School: McMaster University
• Department: Astronomy
• Course: ASTRON 2B03
• Professor: Laura Parker

Document Summary

The number of protons that an atom has, determines which chemical element it is. (and since a normal atom is electrically neutral, it has the same number of electrons as it has protons. ) The simplest element is hydrogen: an atom of one proton and one electron. The next simplest is helium: two electrons, two protons. The third is lithium: three electrons, three protons and so on. The heaviest element which occurs in nature is uranium, with 92 electrons or protons. Still heavier ones have been made in nuclear physics laboratories. Other common elements, with familiar names, are: carbon (6 protons) nitrogen (7 protons) oxygen (8 protons) silicon (14 protons) iron (26 protons) The two most common elements in the universe as a whole (including stars, planets, and all the interstellar gas in space) are the two simplest: hydrogen and helium. Elements heavier than iron are rare, in relative terms. The course material on the origin of the elements explains why!