Electron Basics

1. Electron Basics

2. Atom Review • Protons and neutrons are bound together to make the atomic nucleus • Protons have a positive electrical charge • Neutrons are neutral and have no electrical charge

3. What is an electron? • It is a sub-atomic particle that can be found around the atomic nucleus. • It has a negative electric charge • Its mass is about 2000x less than a proton or neutron

4. Where is an electron? • Danish physicist Neils Bohr proposed the idea that electrons can be found around the nucleus in different energy levels or shells. • One cannot pinpoint the location of an electron, only about where it is in a specific energy level or shell

5. Electron Shells • There are 7 electron shells (How many periods, or rows are on the periodic table?) • Each shell can hold a specific number of electrons • # of elements in the period = # of electrons that shell can hold • Q: How many electrons can the 2nd electron shell hold? • A: 8

6. Electron Shell Capacity - 1st 18 elements • 1st Shell: 2 e- • 2nd Shell: 8 e- • 3rd Shell: 8 e- • Electrons fill each shell from the inside out. Ex: the 1st shell is filled first

7. Valence Electrons • Electrons in the outermost shell are called valence electrons. • They are involved in chemical bonding and reactions. • We will talk much more about these electrons when we talk about chemical reactions in later chapters.

8. Bohr Diagrams • A conceptual model of an atom • # of n and # of p are written in the nucleus (center circle) • # of e- are filled in each shell until it is full (How many can each shell hold?) • Once a shell is full, you add another circle and continue.

9. Bohr Diagram Practice • Pick 3 elements from the first 18 elements, and create Bohr Diagrams for those elements.