1. Atoms & Isotopes NOTES

2. Reading the Periodic Table AEMAEM Atomic Number Average Atomic Mass Element Symbol

3. Reading Atoms & Isotopes E A M Element Name – M Element Symbol Mass Number Atomic Number Or

4. Atomic Number The number of Protons in the nucleus of a given atom Remember – All atoms as a whole want to have a Neutral electrical charge. Atomic #the # of Protons the # of electrons = =

5. Mass Number The sum of the number of protons and number of neutrons in the nucleus of an atom. Example: Carbon - 12 6 n 6 p + 12

6. Isotopes Atoms that have the same number of Protons but different numbers of Neutrons. Example: Bromine - 79 = 35p and 44n Bromine - 80 = 35p and 45n

7. Average Atomic Mass The average mass of all isotopes of an element. Example: In a sample of 100 Carbon atoms: 99 of them are Carbon-12 & 1 is a Carbon-14. What’s the Average Atomic Mass? 12.02

8. Finding the # of Neutrons: # of Neutrons = Mass # - Atomic # Use the formula below: 3 Li 6.94 Name:# p :# e :# n : Lithium 3 3 4

9. Unit of Measurement (MASS): Atomic Mass Unit (amu) one-twelfth the mass of a carbon-12 atom. (6P & 6N) 1 amu = 1.665402 x 10 -27 Kg 1p = 1.007280 amu 1n = 1.008670 amu 1e = 0.000549 amu

10. Practice Problems Element: _________ Symbol: _________ Protons: _________ Protons: ________ Electrons: _________ Electrons: ________ Neutrons: _________ Neutrons: ________ 50 Sn 118.71 Tin 50 69 50 Mg 12 Magnesium-24

11. More Practice Problems Element: _________ Protons: _________ Protons: ________ Electrons: _________ Electrons: ________ Neutrons: _________ Neutrons: ________ Cr 24 52 Au 79 197 Chromium 24 28 24 Gold 79 118 79

12. More Practice Problems Element: _________ Protons: _________ Protons: ________ Electrons: _________ Electrons: ________ Neutrons: _________ Neutrons: ________ Cl 17 37 Cl 17 35 Chlorine 17 18 17 Chlorine 17 20 17