Electron Dot Diagram

1) Drawing electrons dot diagrams

• The nucleus is represented by the atomic symbol
• For individual elements determine the number of valence electrons
• Electrons are represented by dots around the symbol
• Four obitals  (one of each side of the nucleus each holding a max of 2e-)
• Each orbital get 1e- beofre they pair.

  A) Lewis Diagrams for compounds and ions

       In covalent compounds electrons are shared.

1. Determine the number of valence electrons for each atom in the molecule
2. Place the atoms so that the valence electrons are shared to fill each orbital

 B) Double and Triple Bonds

     Sometimes the only way covalent compounds can fill all their valence levels is if they share more than one electron.

 C) Ionic Compounds

• In Ionic compounds electrons transfer from one element to another
• determine the number of valence electrons on the cation. move these to the anion
• Draw [ ] after the metal and non metal.
• Write the charges outside the brackets

Trends on the Periodic Table

- elements close to each other on the periodic table display similar characteristics
          7 IMPORTANT PERIODIC TRENDS
                  1. reactivity
                  2. ion charge
                  3. melting point
                  4. atomic radius
                  5. ionication energy
                  6. electronegativity
                  7. density*

1. Reactivity
- metals and non-metlas how different trends
- the most reactive metal is Francium ; the most reactive non-metal is Flourine

2. Ion charge
- elements ion charge depend on their group (columns)


3. Melting Point
- elements in the center of the table have the highest melting points
- noble gases have the lowest melting points
- starting from the left and moving right, melting point increases (until the middle of the table)
*carbon doesnt follow trend --- highest melting point

4. Atomic Radius
- radius decrease to the up and the right
- Helium has the smallest atomic radius
- Francium has the largest atomic radius

5. Ionization Energy
- ionizatino energy is the energy needed to completely remove an electron from an atom
- it increases going up and to right
- all noble gases have high ionization energy
- helium has the highest ionization energy
- francium has the lowest ionization energy
- opposite trend from atomic radius

6. Electronegativety
- electronegativity refers to how much atom want to gain electrons
- same trend as ionization energy