2. Atomic structure Atoms are made up of 3 types of particles electrons, protons and neutrons. These particles have different properties. Electrons are tiny, very light particles that have a negative electrical charge (-). Protons are much larger and heavier than electrons and have the opposite charge, protons have a positive charge. Neutrons are large and heavy like protons, however neutrons have no electrical charge.

3. Location,size and position of the particles relative massrelative charge proton1+1 neutron1 0 electron 1/1836 -1

4. The nucleus The nucleus is at the center of the atom and contains the protons and neutrons. Protons and neutrons are collectively known as nucleons. Virtually all the mass of the atom is concentrated in the nucleus, because the electrons weigh so little.

6. The electrons Atoms are electrically neutral # of electrons = # of protons So, if an oxygen atom has 8 protons, it must also have 8 electrons; if a chlorine atom has 17 protons, it must also have 17 electrons. The electrons are found at considerable distances from the nucleus in a series of levels called energy levels

7. Finding the number of subatomic particles # of protons = ATOMIC NUMBER of the atom

8. Finding the number of subatomic particles Protons = the atomic number Electrons = the protons (the atomic number) Neutrons =  Mass number - atomic number = neutrons Use a periodic table for this

9. Examples Find the atomic # for Hydrogen Atomic is 1  Therefore Hydrogen has 1 P+ & 1 e- Neutrons  Mass # - atomic # = neutrons  So H has no (0) neutrons You try for Li (lithum)

10. Answer for Li Atomic # = 3 P+ & 3e- Neutrons  Mass # - atomic number  7 - 3 = 4 neutrons =(No)  Book reference  Chapter 10