1. Structure of the Atom Sections 17.1-17.4

2. Review Elements are made up of only one type of atom. All elements are listed on the Periodic Table. Each element is represented by its atomic symbol.

3. Atomic Symbols Some symbols come from the elements name. –Example: C is for Carbon Others come from the element’s Latin name. –Example: Au is for Gold (aurum) Pb is for Lead (plumbum)

4. About Atoms Atoms are so small they can’t be seen with visible light. Photographs of atoms can be seen by a scanning tunneling microscope. The atom is actually made up of smaller subatomic particles. –Proton –Electrons –Neutrons

5. The Nucleus Nucleus contains protons and neutrons. The electrons can be found surrounding the nucleus in the electron cloud. Electrons are very far away from the nucleus. There is actually a lot of empty space between the nucleus and electrons.

6. Subatomic Particles ParticleChargeMass Compared to an Electron Actual Mass Electron19.11 x 10 -31 Proton+118361.673 x 10 -27 Neutron018411.675 x 10 -27

7. Isotopes The number of protons tells us the atomic number of the atom. The mass number is the total number of protons and neutrons in the nucleus. Atoms can have different numbers of neutrons. Atoms that have different numbers of neutrons are called isotopes.

8. Isotopes There are three known isotopes of Hydrogen. HHHHHH 1 1 11 2 3 1 proton 0 neutrons 1 proton 1 neutron 1 proton 2 neutrons

9. What do these numbers mean? Li 3 7 Mass Number Atomic Number How many protons does lithium have? How many neutrons does lithium have? Element Symbol

10. Atomic Mass The atomic mass is NOT the same as the mass number. The atomic mass shown on the periodic table is an average of all the isotopes of that element.