Daily ScienceName the following:

HBrH2SO3

P3O5

Label the following as being an ionic bond or covalent bond:NaClIron (III) oxideDinitrogen pentoxideCa3(PO3)2

PCl5

Lewis StructuresPg. 55

Structural FormulasUsed to show relative positions of atomsUse lines for bondsStructural formulas are made from Lewis

structures

Symbols for Lewis structures = an electron = an electron pair (lone pair) = single bond (σ bond)- 2 electrons = double bond (σ and π)-4 electrons = triple bond (σ and 2 π)- 6 electrons

Steps for drawing Lewis Structures1. Determine the number of valence electrons for each

element1. Sum the valence electrons for all the elements

2. Determine which atom will be the central atom and connect each element with a line.

1. H and halogens are always terminal2. Least electronegative is the central atom3. First atom listed is USUALLY the central atom

3. Each atom (except H and He) must have 8 electrons around it (octet). Complete each octet by adding lone pairs.

4. Count the number of electrons in your structure1. Too many electrons, cross out a lone pair from the central

atom and a terminal atom (except H and He) and create a multiple bond

2. Recount and repeat until the total number of electrons equals the number from number 1

ExamplesCCl4

NF3

CO

Expanded valenceIf your total number of electrons in the last

step is less than the total in number 1, add a lone pair around the central atom.

This can occur from the 3rd period downCalled an expanded valenceEx. SeCl4 and PCl5

Lewis structures of ionsDo the same steps and add the extra

electrons that are with the ionIf the ion is positive, subtract electronsIf the ion is negative, add electronsEx. SO4

2-

PracticePg. 56

Create a chart like the following taking up the WHOLE pageFormula Total

Valence Lewis Structure

# of σ bonds

# of π bonds

CO32-

NO3-

H2S

H3O+

PO3-3

PF5

ClCN

CH2O

OF2

H2O