1. Atoms

3. Greek Atomic Model Democritus (400 BC)Democritus (400 BC) Named the atomNamed the atom Atom cannot be dividedAtom cannot be divided

4. Dalton’s Atomic Theory 18031803 All elements are composed of atoms (not divisible)All elements are composed of atoms (not divisible) Atoms of same element are the sameAtoms of same element are the same Atoms of different elements are differentAtoms of different elements are different

5. Thomson’s Model 18971897 Atom has smaller parts, like electronsAtom has smaller parts, like electrons Atom made of a positive pudding-like material with negatively charged electrons scattered throughoutAtom made of a positive pudding-like material with negatively charged electrons scattered throughout

6. Rutherford’s Model 19111911 Positive-charged particles in the nucleusPositive-charged particles in the nucleus Negative scattered around edgesNegative scattered around edges Gold foil experimentGold foil experiment

7. Rutherford’s Experiment

8. Bohr’s Model 19131913 Electrons move in definite orbits around the nucleus (like the planets move around the sun)Electrons move in definite orbits around the nucleus (like the planets move around the sun) Energy levels located a certain distance from the nucleusEnergy levels located a certain distance from the nucleus

9. Compare the Thomson to the Rutherford/Bohr

10. Wave Theory Modern modelModern model Electrons do not travel in definite pathsElectrons do not travel in definite paths Think electron cloudThink electron cloud

11. Atomic Structure

12. Subatomic Particles protons = positive charge (+)protons = positive charge (+) electrons = negative charge (-)electrons = negative charge (-) neutrons = neutral (0 charge)neutrons = neutral (0 charge)

13. Subatomic Particles

14. Lithium Atom How many protons?How many protons? How many electrons?How many electrons? How many neutrons?How many neutrons?

15. Atomic Number identifies the element on the periodic tableidentifies the element on the periodic table equals the # of protons in the nucleusequals the # of protons in the nucleus

16. Atomic Mass sum of the # of protons + # of neutrons in the nucleussum of the # of protons + # of neutrons in the nucleus changes with isotopeschanges with isotopes

17. Isotopes atoms of the same elementatoms of the same element same # of protonssame # of protons different # of neutronsdifferent # of neutrons different atomic massdifferent atomic mass examples = hydrogen, carbon, uraniumexamples = hydrogen, carbon, uranium

18. Isotopes

19. Electron Cloud electrons move about the nucleus locked in a certain area of the electron cloudelectrons move about the nucleus locked in a certain area of the electron cloud location called energy levelslocation called energy levels

20. Electron Shells

21. # of electrons in each orbital shell electrons with low energy are found in the energy level closest to the nucleuselectrons with low energy are found in the energy level closest to the nucleus