The document discusses Lewis dot structures, which use dots to represent valence electrons around an atomic symbol. It explains that ions have Lewis dot diagrams with fewer (for cations) or more (for anions) dots than the corresponding atom due to gaining or losing electrons. The document provides examples of Lewis dot diagrams for various ions, such as Ca2+ and O2-. It also includes practice problems asking students to draw Lewis dot diagrams for additional ions.

1. AIM: How to write Lewis
Dot Structures (Electron
Dot Structures)
DO NOW:
1. READ BOTH SIDES OF THE HANDOUT.
2. WRITE THE ELECTRON CONFIGURATION (ORBITAL NOTATION)
OF PHOSPHORUS ATOM, AND PHOSPHORUS ION.
3. DRAW THE LEWIS DOT STRUCTURE FOR THE ATOM AND THE
ION.

2. Valence Electrons
Valence Electrons are the electrons in
the highest occupied energy level of
an atom
You can tell the number of valence
electrons from the group number

3. Octet Rule
Octet rule says that atoms like to have
full outer shells of only eight electrons.
Atoms will lose or gain valence
electrons to make their outer shells full
with eight electrons, and they do this
by bonding with other atoms.

4. Lewis Dot Structure (Electron Dot
Structure)
A Lewis dot structure is a quick and
easy diagram that shows the valence
electrons in an element. In a Lewis
structure, the nucleus of the element is
represented by its symbol. The valence
electrons are represented by dots placed
around the symbol in pairs.

5. Rule #1. No side can have
more than two dots because
each orbital can only hold
two electrons.
Rule #2. When filling the
sides of the element symbol
each side gets one dot
before doubling up.
Exceptions are hydrogen
helium.

6. Across Period 2

7. Formation of Cations
A positively charged ion
Na  Na+ + e-

8. Mg  Mg2+ + 2e-

9. Formation of Anions
Negatively charged particles
Cl + 1e-  Cl -

10. What is the Lewis electron dot diagram
for each ion?
Ca2+
O2−

11. Solution
 Having lost its two original valence electrons, the
Lewis electron dot diagram is just Ca2+.
Ca2+
 The O2- ion has gained two electrons in its valence
shell, so its Lewis electron dot diagram is as follows:

12. SUMMARY
Lewis electron dot diagrams use dots to
represent valence electrons around an atomic
symbol.
Lewis electron dot diagrams for ions have less
(for cations) or more (for anions) dots than the
corresponding atom.

13. PRACTICE QUESTIONS
1. Draw the Lewis electron dot diagram for each
element.
bromine
gallium
2. Draw the Lewis electron dot diagram for each
ion.
Mg2+
S2−

14. State the number of valence electrons
and draw the Lewis Structure of the
following ion:
1. P 6. C+2
2. O+2 7. Zn +2
3. Ba 8. W+6
4.At 9. Cu+1
5. Ba+2 10. F-1