1. Matter  Molecules  Atoms  protons + neutrons + electrons  quarks and leptons  Molecules  Atoms  protons + neutrons + electrons Realm of Chemists The Atom Rutherford STM - scanning tunneling microscopy (of Si) JJ Thomson Particle Mass Charge Electrons 9.11x10 -31 kg -1 Protons 1.67x10 -27 kg+1 Neutron 1.67x10 -27 kg 0 Tutorial Structure of the Atom

2. A. Atomic Number (Z) = #protons in an atom’s nucleus C. Mass Number (A) = # of protons + # of neutrons X AZAZ Atomic number Mass number Element 1. Isotopes - atoms of the same element with different numbers of neutrons (same Z different A) B. Element - a substance whose atoms all have the same number of protons D. Atomic Symbols Atomic Number (Z)

3. Exercises Additional Tutorial