1. Cl Cl Br Br I I #7 Draw electron dot structures for each molecule
UNSHARED PAIRS
First step is to place the
correct number of valence
electrons on the drawing.
a. chlorine
Cl Cl
Chlorine shares two
electrons with another
chlorine.
Second step is to show
sharing of electrons.
b. bromine
Br Br
I I
c. iodine
a diatomic
molecule; Br2
I2 Cl2 etc.

2. a. H2O2 b. PCl3 #8 The following molecules have single covalent bonds.
Draw an electron dot structure for each.
a. H2O2 H O O H Cl
b. PCl3 P Cl Cl

3. #9 Draw the electron dot structure of the hydroxide ion OH--1 O H
Note that the hydroxide ion has
one extra electron than the total
you expect form oxygen and
hydrogen alone (6+1=7).
Electron #8 came from another
atom that donated it to the hydroxide
ion.

4. #10 Draw the electron structure of the
polyatomic boron tetrafluoride anion
(BF4-1) F F B F F
notice that one extra electron (shown as the
yellow on in this picture) is needed
to complete the molecule. That is why
BF4 has a negative one charge.
3D view of BF4

5. #11 Draw the electron dot structures for sulfate (SO4)-2
and carbonate (CO3)-2. Sulfur and Carbon are the
central atoms, respectively. O
1. put in the valence electrons that each atom
has, be sure to add two extra electrons (yellow)
due to the negative 2 charge on this
molecule. S O O O
sulfate (SO4) -2

6. DONE! O S O O O sulfate (SO4) -2
#11 Draw the electron dot structures for sulfate (SO4)-2
and carbonate (CO3)-2. Sulfur and Carbon are the
central atoms, respectively. O
2. arrange the electrons so as to best fulfill
the octet rule. S O O
DONE! O
sulfate (SO4) -2

7. #11 Draw the electron dot structures for sulfate (SO4)-2
and carbonate (CO3)-2. Sulfur and Carbon are the
central atoms, respectively. O
1. put in the valence electrons that each atom
has, be sure to add two extra electrons (yellow)
due to the negative 2 charge on this
molecule. C O O
carbonate (CO3) -2

8. DONE! O C O O carbonate (CO3) -2
#11 Draw the electron dot structures for sulfate (SO4)-2
and carbonate (CO3)-2. Sulfur and Carbon are the
central atoms, respectively. O
2. arrange the electrons so as to best fulfill
the octet rule. C O O
DONE!
carbonate (CO3) -2

9. O C O O H #12 Draw the electron dot structure for the hydrogen
carbonate ion (HCO3)-1 Carbon is the center atom,
and hydrogen is attached to oxygen in this polyatomic
anion. O
1. put in the valence electrons that each atom
has, be sure to add one extra electron (yellow)
due to the negative 1 charge on this
molecule. C O O H

10. DONE! O C O O H hydrogen carbonate (HCO3) -1
#12 Draw the electron dot structure for the hydrogen
carbonate ion (HCO3)-1 Carbon is the center atom,
and hydrogen is attached to oxygen in this polyatomic
anion.
2. arrange the electrons so as to best fulfill
the octet rule. O C O O
DONE! H
hydrogen
carbonate (HCO3) -1