Chapter 1: Periodic Table, Lewis Structures, Bonding, Formal Charge

Chem 203, Review

Which row in the periodic table will want to form complete octets? How will it achieve the complete octets?

Elements in the SECOND row; will form either ionic or covalent bonds

How is the electron configuration written for an element?

-Look for the ATOMIC number of the element

-Use following energy levels:

1s

2s 2p

3s 3p 3d

4s 4p 4d 4f

How many electrons can be held in each level?

-s=2

-p=4

-d=6

-f=10

How are sigma bonds formed?

They are formed by HEAD to HEAD overlap of P orbitals

How are pi bonds formed?

They are formed via SIDEWAYS overlap of P orbitals

Which bond, between sigma and pi, is stronger and why?

Sigma bonds are stronger since there is HEAD TO HEAD overlap

What are the steps for determining Lewis structure?

-Find sum of VALENCE electrons of polyatomic ion/molecule

-If P.A. ion/molecule has a - or + charge, add or subtract electron as necessary

-Place LEAST electronegative atom in CENTER

-Connect central atom to MORE ELECTRONEGATIVE atoms with single bonds

-Fill octet of OUTER atoms

-Fill octet of CENTRAL atom

How is formal charge calculated?

Number of valence electrons in FREE atoms - bonds and dots