Structure of the Atom PSC Ch. 3-2

The Atom Subatomic particles The nucleus The notation and the periodic table Isotopes and Ions Determining atomic mass

Subatomic Particles Electrons Discovered by J.J. Thompson Discovered how: Cathode ray tubes-rays traveled from cathode to anode, bent by electric and/or magnetic field, caused paddle wheel to turn Vital Stats… Mass: 9 X 10-31 kg , ~1/2000 mass of p+, .00055u Charge: -1, -1.30x10-19c, Location: electron cloud / outside nucleus

Subatomic Particles Protons Discovered by J.J. Thompson Discovered how: Modified cathode ray tube particles traveled from anode to cathode Vital Stats: Mass: 1.673 X 10-27 kg; ~2000x mass of e-, 1.007u Charge: +1, 1.60x10-19c Location: nucleus

Subatomic Particles Neutrons Discovered by James Chadwick Discovered how: High energy beam unaffected by magnetic or electric fields Vital Stats: Mass: 1.675 X 10-27 kg (very similar to the proton) Charge: 0, neutral Location: in the nucleus

The Nucleus Discovered by Lord Ernest Rutherford Discovered how : Gold foil experiment- + charged particles shot at thin gold foil. Most went straight through, some deflected. Very few bounced straight back Small dense + charged core in atom (atom is mostly empty space) Vital Stats: + charge Dense – over 99% of the atom’s mass 1/trillionth the volume of the atom

Graphic Organizer ATOM e- cloud Nucleus -Most of volume -99% of mass -Very little mass Nucleus -99% of mass -1/trillionth of volume e - (electrons) -.0005u -neg charge, -1 -J.J. Thompson -cathode ray tube p+ (protons) -modified cathode ray tube -positive charge, +1 -1.007u no (neutrons) -James Chadwick -no charge -1.009u

Isotopes Sometimes atoms of the same elements have a different number of neutrons All elements have isotopes! And they exist in different abundances.

Ions (p. 161) Sometimes atoms will gain or lose electrons Too many : negative charge Too few: positive charge