Molecules and Compounds Valence Electrons, Octet Rule, and Lewis Dot Structures

ESSENTIAL QUESTION Explain why the valence electrons are important when looking at the periodic table.

Atoms combine to make molecules Most atoms are unstable unless combined with other atoms to make molecules and compounds!! Molecules Why combine?

Formed when atoms combine Electrons in the outermost part of the electron cloud surrounding the nucleus. The ones that do the bonding!! Chemical Bond Valence e-

There are many energy levels around the nucleus Can hold up to 2 electrons What element is this??? Energy Levels First E.L.

Second E.L. What element is this?? Third E.L. Can hold up to 8e- Can hold up to 8e-!

Atoms form bonds to complete their octet (8 e-) and become stable Have 8 valence electrons! Octet Rule Chemically-stable atoms

Complete this chart:

Elements in each group have the same number of valence e- with the exception of the transition metals Use P.T. to find Valence e-

Represent the valence e- Represents nucleus and all e- except for valence e- Each dot = 1 e- Dot Diagrams Element Symbol Up to 8 dots

Examples: H C Cl Mg N Ar Al O

Reflection: How do we write Dot structures Reflection: How do we write Dot structures? Why are valence e- important?