1. Electron Configuration
Shorthand electron configuration

2. Using shorthand electron configurationNa
1s2 2s2 2p6 3s1 Ca
1s2 2s2 2p6 3s2 3p6 4s2
Shortcut of electron configuration using noble gases
[Ne] 3s1
[Ar] 4s2
Normal electron configuration
Shorthand electron configuration

3. Ions

4. What are Ions?
Atoms can gain or lose electrons.
If an atom gains or loses electrons, it will obtain a charge
Ions are charged atoms.

5. Types of Ions: Cations and Anions
If Na lost an electron what is its charge?
If Ca lost 2 electrons what is its charge?
Atoms with a positive charge
Atoms that have lost electrons
Na+
Ca 2+

6. Types of Ions: Cations and Anions
If S gains two electrons, what is its charge
Atoms with a negative charge
Atoms that have gained electrons
S2-

7. Valence Electrons

8. What is a valence electron?
Valence electrons are the electrons in the highest occupied energy level of an element’s atoms.
Cl = 1s2 2s2 2p6 3s2 3p5
Cl has 7 electrons in its last energy shell.
Number of valence electrons largely determines the chemical properties of an element.

9. What is a valence electron?
Valence electrons are also related to the group numbers of the periodic table.
1A valence electron
2A valence electrons
3A valence electrons
4A valence electrons
5A valence electrons
6A valence electrons
7A valence electrons
8A valence electrons
Helium is the exception
It has 2 valence electrons

10. Ca : Valence electrons What is the electron dot structure of S ?
Valence electrons are usually the only electrons used in chemical bonds.
Valence electrons are usually shown in electron dot structures.
Example: Ca
Ca : ..
: S :

11. Electron Configuration in Chemical Bonding
The Octet Rule
In forming compounds, atoms tend to achieve the electron configuration of a noble gas.
Octet = a set of eight
ns2 np6

12. Electron configurations for Cations
Cations are atoms with a positive charge
Metals tend to become cations.
Metals tend to lose their valence electrons, leaving a complete octet in the next-lowest energy level.
What is a Cation?
Metals

13. Electron Configurations for Anions
Nonmetals
Nonmetals tend to gain electrons since they have their last energy level almost full, it is easier to gain electrons than to lose them.
Nonmetals tend to form anions
Anions are atoms with a negative charge