1. Parts of the Atom … from Discovery to Reality

2. NUCLEUS PROTONS ✚ Positively charged particles Mass = 1 amu NEUTRONS No charge or neutral Mass = 1 amu OVERALL CHARGE OF NUCLEUS = ✚ ✚ ✚

3. What is amu? ATOMIC MASS UNIT 1/12 the mass of the carbon 12 atom Carbon-12 was assigned the amu = 12 Every other element is relative to this assignment Just a unit – like grams, pounds, milliliters

4. OUTSIDE THE NUCLEUS ELECTRONS Negatively charged Neglible mass (very little mass) Electrons found in DENSE FUZZY CLOUDS!

5. ATOMIC NUMBER Atomic Number = # of PROTONS On the periodic table, the atomic number is IN BLUE. In a neutral atom: # protons = # of electrons 19 55 16 23

6. MASS NUMBER Where is all the mass of an atom? Mass Number = # of protons + # of neutrons On the periodic table, the mass number is the RED number ROUNDED. 4 4 95 10 4 2010 11 23 12

7. NOTATION TYPES HYPHEN NOTATION NUCLEAR SYMBOL Au-197

8. What is an isotope? Isotope = atoms that have the same number of protons but different number of neutrons. – chemically alike but with varying mass numbers

9. What is the average human mass? 50 7073 85 94lbs Average = 74.4 lbs

10. Average Atomic Mass of all naturally occurring isotopes

11. What is atomic mass? Atomic Mass or Atomic Weight - average of the masses of its naturally occurring isotopes EX. You have a box containing two sizes of marbles. 25% of the marbles have a mass of 2 g. 75% of the marbles have a mass of 3 g. Calculate the average mass of the marble. (0.25 x 2 g ) + (0.75 x 3 g) = 2.75 g

12. EX. Copper has two naturally occurring isotopes: Cu-63 (69.17% abundant) with amu = 62.929 Cu-65 (30.83% abundant) with amu = 64.927 Calculate the average atomic mass. (0.6917 x 62.929 amu ) + (0.3083 x 64.927 amu) = 63.55 amu