Atomic Structure and the Periodic Table›1a. Atoms, Elements, Compounds and Mixtures›Isotopes
Lesson 03 of 14
Isotopes
Key Concepts
- Isotopes
- Proton number vs mass number
- Neutrons
- Isotope notation: element name + mass number
- Relative atomic mass
- Weighted average calculation
- Isotope abundance
- Stable isotopes
- Radioactive isotopes
- Beta decay
- Carbon dating
- Carbon-12 reference standard
Checking the Basics
If you're watching this video as part of your chemistry course, then you might find it helpful to be able to answer these questions before continuing.
What are the three particles found inside an atom?+
Protons, neutrons, electrons
Which two particles are found in the nucleus?+
Protons and neutrons
How many protons are present in an atom of oxygen? a) 16 b) 8 c) 24+
b) 8
Lesson notes
Chlorine's relative mass of 35.5 is the perfect puzzle to open this topic — it can't be a single whole-number mass, so what's going on? This video answers that question by introducing isotopes: atoms of the same element with different numbers of neutrons. You'll learn how to write isotope notation, calculate relative atomic mass as a weighted average, and see why radioactive isotopes like carbon-14 have real-world applications from carbon dating to medical imaging.
What You Will Learn
01:39What isotopes are and how they differ from each other in terms of neutron number.
01:53How to write isotope notation using element name plus mass number.
02:57What proton number and mass number represent and how to calculate neutron count from them.
03:43What relative atomic mass is and why it is not always a whole number.
04:20How to calculate relative atomic mass as a weighted average of isotope masses.
04:46What isotope abundance means and how to interpret abundance data from tables or graphs.
07:38What makes some isotopes stable and others radioactive.
09:04What beta decay is and how it changes the composition of a nucleus.
09:24How carbon dating uses carbon-14 decay to determine the age of organic materials.