diff --git a/302. NUCE 2100 - Fundamentals of Nuclear Engineering/2024-08-27 Introduction.md b/302. NUCE 2100 - Fundamentals of Nuclear Engineering/2024-08-27 Introduction.md
index 5fbc8b8d..d6bdce4f 100644
--- a/302. NUCE 2100 - Fundamentals of Nuclear Engineering/2024-08-27 Introduction.md	
+++ b/302. NUCE 2100 - Fundamentals of Nuclear Engineering/2024-08-27 Introduction.md	
@@ -40,4 +40,9 @@ $^{235}_{92} U$ $^4_2 He$ $^1_1 H$
 **Nuclide** - A type of atom characterized by the number of protons and neutrons in the nucleus of every atom of this type
 **Isotopes** - Atoms with the same number of protons but containing different numbers of neutrons.
 **Isotopic Abundance** - The percentage of an element that is a certain isotope. Sometimes abbreviated (a/o)
+**Atomic Weight** - The average weight of all isotopes weighted by their prevalence.
 
+*Atomic Weight of $^A Z$   = $12 \frac{m\left(^A Z\right)}{m\left(^{12}C\right)}$ . 
+Atomic mass of Z is in the slides
+
+**Molecular weight** is the total mass of a molecule relative to the mass of a neutral $^{12}C$. 
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