1. THE STRUCTURE OF ATOMS Pg. 43

2. Daily science- pg. 40  Who discovered the neutron? Electron? Nucleus?  What did Democritus theorize?  Name two differences between the old atomic theory and the new atomic theory?

3. What makes up an atom?  Atoms are made of subatomic particles.  The three subatomic particles are the proton, electron, and neutron.

4. Structure of an atom  The nucleus is located at the center of the atom.  It contains positively charged particles, called protons, and neutral particles, called neutrons.  Most of the mass is located here.

5. Structure of an atom  Electrons, or negatively charged particles, exist outside of the nucleus in the electron cloud.

6. Subatomic Particles chart ParticleChargeMassLocation Proton+ 11.67 x 10 27 In the nucleus Neutron 01.67 x 10 27 In the nucleus Electron9.11 X 10 31 Outside the nucleus

7. Atomic Number  The periodic table can be used to find the number of protons, electrons, and neutrons.  The atomic number of an element (labeled Z) tells you how many protons there are.  On the periodic table, the elements are listed as neutral elements so the number of electrons=the number of protons.

8. Atomic number Z

9. Mass Number  The mass number (labeled A) is the number of neutrons + protons.  It is located under the element symbol.  You can find the number of neutron by subtracting the Atomic number (Z) from the Mass number (A)  A-Z = # of neutrons

10. Mass Number

11. Writing Atomic mass and number  There is a way to represent atomic mass and number  Steps:  1-start with the element symbol  2- place the mass number on the top left side of the symbol  3-place the atomic number on the bottom left side of the symbol

12. Symbol Al 27 13

13. Isotopes  An isotope is an element that has the same number of protons but a different number of neutrons.  Ex. Carbon has 2 common isotopes:  Carbon-12 Carbon-14  The numbers represent the mass number

14. Determining the number of neutons  Ex. Carbon 12 and Carbon 14