Concept of mole/molar ratio
1) How many moles of sodium atoms correspond to 1.56x1021 atoms of
2) How many moles of Al atoms are needed to combine with 1.58 mol of
O atoms to make aluminum oxide, Al2O3?
3) How many moles of Al are in 2.16 mol of A
For many molecules and ions, no single Lewis structure
provides a truly accurate representation.
Three Lewis strictures for the carbonate ion.
Linus Pauling - 1930s
Many molecules and ions are best described by
writing two or more Lew
2 KClO3 (s) 2 KCl (s) + 3 O2 (g)
1. How many grams of O2 is produced if 2.50 g of KClO3 is completely decomposed by heating?
x g O2 = 2.5 g KClO3 x (1 mol KClO3) x (3 mol O2) x (32 g O2) = 0.98 g O2
(122.5 g KClO3) (2 mol KClO3) (1 mol O2)
Lewis Model of Bonding
In 1916, Gilbert N. Lewis pointed out that the lack of
chemical reactivity of the noble gases indicates a high
degree of stability of their electron configurations.
The Octet Rule
Octet rule: The tendency of group 1A-7A elements to