Crash Course is a YouTube series that gives an middle school friendly and understandable break down of a wide variety of science topics. This video worksheet accompanies Chemistry: #1 The Nucleus, and is an excellent introduction to Chemistry, the nucleus, subatomic particles (protons, neutrons, and electrons), atomic mass and isotopes.. This 19 questions video worksheet is perfect as an introduction to chemistry, for use with early finishers and for filling time on half days, or as sub-work whe