1. Notes #3 Introducing………The Atom!

2. History of the Atom A. Democritus (400 BC) – 1. Said matter is made of invisible particles called atoms – 2. The atoms were “indivisible” or “uncuttable”

3. WHAT IS AN ATOM? Atoms are the basic particles from which everything IN THE ENTIRE UNIVERSE is made. There are only 92 naturally- occurring different types of atoms known to exist. Each type of atom is different from all of the others. Atoms are so small that your paper is over 1 million atoms thick!

4. An electron microscope image of an atom

5. Atom nucleus Shells, clouds, orbitals protons neutrons electrons

6. Where do all the parts go? Copy the chart below Subatomic particle Atomic mass in atomic mass units chargelocation Proton Neutron Electron

7. WHAT ARE THE PARTS OF AN ATOM? 1. The nucleus- NUCLEUS MEANS CENTER Contains the particles called protons and neutrons clustered together

8. A. The Protons Charge: positive Mass: 1 AMU (atomic mass unit) 1 AMU = 1.66 x 10 -24 grams or. 00000000000000000000000166 grams Importance: Protons give an atom its identity

9. B. the Neutrons Charge: neutral (no charge) Mass: 1 AMU, about the same size as a proton Importance- neutrons keep the nucleus from blowing apart

10. A typical model of the nucleus of an atom Sketch this +

11. 2. The electron shells- where the electrons are found ELECTRONS Charge: negative (-) Mass: 0 AMU- too small to contribute to the overall mass of the atom Importance: give the atom its “Personality”

12. Where do all the parts go? Fill in the chart below Subatomic particle Atomic mass in atomic mass units chargelocation Proton1+ positive nucleus Neutron1 amuneutralnucleus Electron0Negative - Orbits around nucleus in “shells”

13. A typical model of the electron shells or clouds electrons

14. HOW CAN YOU IDENTIFY WHICH TYPE OF ATOM IS WHICH? Each different type of atom has a different number of protons.

15. Examples : if it has one proton, it is always Hydrogen 1

16. Helium atom

17. How do you know how many electrons an atom has? In a neutral atom: # of electrons = # of protons

18. Summary: Protons and neutrons are found in the nucleus in the center of an atom Electrons are found in “shells” or “orbitals” outside the nucleus. The number of electrons equals the number of protons

19. How do you know how many electrons an atom has? In a neutral atom: # of electrons = # of protons

20. Summary: Protons and neutrons are found in the nucleus in the center of an atom Electrons are found in “shells” or “orbitals” outside the nucleus. The number of electrons equals the number of protons

21. What is an atom’s atomic number? Each type of atom has a different atomic number Atomic number =number of protons atomic number identifies the element

22. What is an isotope? Isotopes : Atoms of the same element with different numbers of neutrons

24. What is atomic mass ? Atomic mass is the total mass = protons + neutrons

25. Atomic mass of hydrogen isotopes