Grade 10 CBC Chemistry | isotopes and relative atomic mass: why is chlorine 35.5?

Every chlorine atom has a mass number of 35 or 37, so why does the periodic table say 35.5? In this Grade 10 CBC Chemistry lesson you will learn what isotopes are, read the symbol of an isotope and count its particles, see why isotopes react in the same way, and calculate relative atomic mass in three steps. You will also learn to work backwards: finding the percentages, or a missing mass number, from the relative atomic mass. A FREE REVISION PAPERS FOR THIS LESSON Paper 1: Core concepts Download them here: https://drive.google.com/file/d/1VhkI... The marking scheme will be in the description of Video 3, so try the paper on your own first. MARKING SCHEMES FOR VIDEO 1: Did you try the revision paper from Video 1 (What is inside an atom?)? Mark your work here: https://drive.google.com/file/d/1nuTn... IN THIS VIDEO 0:00 Hook and title 0:25 In this video 1:01 Two kinds of carbon atom 1:40 Three isotopes of hydrogen 2:07 Spotting isotopes from symbols 3:03 Your turn: chlorine-37 3:47 Why isotopes react the same way 4:24 Relative atomic mass 5:02 A bag of 100 chlorine atoms 6:05 Why not 36? 6:45 The three-step method 7:15 Worked example: magnesium 8:24 Your turn: boron 9:17 Working backwards: finding the percentages 10:56 Your turn: bromine 12:12 Working backwards: a missing mass number 13:25 Your turn: neon 14:31 Watch out for these mistakes 15:15 What to remember 15:51 Challenge and next video YOUR CHALLENGE Lithium is 7.5% lithium-6 and 92.5% lithium-7. Calculate its relative atomic mass to one decimal place, and write your answer in the comments. PREVIOUS VIDEO Video 1: What is inside an atom?    • Grade 10 CBC/CBE Chemistry | What is insid...   NEXT VIDEO Video 3: s and p orbitals. What is really inside an energy level? Coming soon. ABOUT SP-SciLearn SP-SciLearn makes paced, interactive science lessons for Kenyan learners following the CBC. Every video stops so that you can try a question yourself before the answer appears. Subscribe and turn on notifications so that you do not miss the next lesson. Grade 10 CBC Chemistry · 1.2 The Atom #Grade10Chemistry #CBCKenya #Chemistry