2.  Atoms  Elements are made of particles called atoms  Atoms are the smallest pieces of matter that contain all the properties of a specific element  Each element contains only one type of atom  Inside the Atom  Atoms are made up of smaller particles  These particles are found in different regions of the atom

3.  Protons  Positively charged particles found in nucleus of atom  Have an electrical charge of +1  Mass of 1 a.m.u. (1.67x10 -27 kg)  Neutron  Neutral particles found in nucleus of atom  Have no electrical charge  Mass of 1 a.m.u.  Electron  Negatively charged particles found in electron cloud  Have an electrical charge of -1  Constantly moving around outside nucleus  Much Lighter (9.11x10 -31 kg)

4. Structure of the Periodic Table  Atomic number – Tells us how many protons and electrons are in an atom  The number of protons defines the identity of the atom  Atomic Mass – gives the mass of a single atom in atomic mass units (amu)  Atomic mass = p + + n 0

5. Symbols  Elements are listed by their chemical symbols  Symbols are usually either one capital letter like C for Carbon, or one capital and one lowercase letter like Ne for Neon

6. Periodic Table  The periodic table gives much information we need to learn more about the atom of each element

7. Atomic Mass  The average atomic mass is the number at the bottom of this square  Found by averaging the natural abundances of its isotopes  Mass # = # p + + # n 0

8. Atom Math Atomic Number Symbol Element Name Atomic Mass

9. Atom Math ProtonsElectrons ProtonsNeutrons

10. Practice 30 8 15.999 8 8 8 Zn Oxygen 65.39 30 35 30 Lithium 3 6.941 3 4 3 # n 0 = Mass # - Atomic #

11. Isotopes  Atoms of the same element with different mass numbers. Mass # Atomic #  Nuclear symbol:  Hyphen notation: carbon-12

12. Isotopes © Addison-Wesley Publishing Company, Inc.