Energy Levels, Electrons, and the Periodic table You NEED to be referring to the periodic table while reading these notes! Get it out! Look at it!

Energy levels 1 st energy level can hold 2 electrons 2 nd energy level can hold 8 electrons 3 rd energy level can hold 18 electrons 4 th – 7 th energy levels can hold 32 electrons

Octet Rule The valance energy level (the outermost energy level) can only hold 8 electrons. When the 3 rd – 7 th energy levels are NOT the valance, they can hold more than 8. For example, when the 4 th energy level is the valance, the 3 rd can now hold 18.

Periodic Table The row number of the element tells you WHAT ENERGY LEVEL IS VALANCE. The row number does NOT always tell you what energy level each atom is currently putting electrons in.

1 st Row Represent the 1 st energy level, which can only hold two electrons. Hydrogen is putting the first electron in the 1 st energy level. Helium is putting the 2 nd electron in the 1 st energy level. The 1 st energy level is FULL with Helium.

2 nd Row Represents the 2 nd energy level, which can hold 8 electrons. Lithium is putting the 1 st electron in the 2 nd energy level. Beryllium is putting the 2 nd electron in the 2 nd energy level. Boron is putting the 3 rd electron in the 2 nd energy level.. Ect.. To Neon, which is putting the 8 th electron in the 2 nd energy level. The 2 nd energy level is FULL with Neon.

3 rd Row Represents the 3 rd energy level as valance – but does not FILL the 3 rd energy level, because the 3 rd energy level can hold 18 electrons, but only 8 elements are on the 3 rd row. Sodium is putting the 1 st electron on the 3 rd energy level. Magnesium is putting the 2 nd electron on the 3 rd energy level… ect. To Argon, which is putting the 8 th electron on the 3 rd energy level. At Argon, no more electrons can go on the 3 rd energy level at this time because it is currently the valance.

4 th Row Represents that the 4 th energy level is valance. Potassium is putting the 1 st electron on the 4 th energy level; Calcium is putting the 2 nd electron on the 4 th energy level (*4 th energy level is now valance). Scandium is putting the 9 th electron on the 3 rd energy level (since the 3 rd is no longer the valance at this point, it can now hold 18 electrons.) Titanium is putting the 10 th electron on the 3 rd energy level.. Ect… to Zinc, which is putting the 18 th electron on the 3 rd energy level. At this point, the 3 rd energy level is now FULL.

4 th Row (cont) Gallium goes back to putting electrons on the 4 th energy level, so it puts the 3 rd electron on the 4 th energy level…. To Krypton, which puts the 8 th electron on the 4 th energy level. At this point, the 4 th energy level is the valance, so even though it can hold 32 electrons, no more electrons can be on the 4 th energy level at this time. The 4 th energy level will not be full until the 6 th row!

5 th Row Represents that the 5 th energy level is valance. Rubidium is putting the 1 st electron on the 5 th energy level; Strontium is putting the 2 nd electron on the 5 th energy level (*5 th energy level is now valance). Yttrium is putting the 9 th electron on the 4 th energy level (since the 4 th is no longer the valance at this point, it can now hold more than 8 electrons.) Zirconium is putting the 10 th electron on the 4 th energy level.. Ect… to Cadmium, which is putting the 18 th electron on the 4 th energy level. At this point, the 4 th energy level is NOT yet full, but the next electron will not go on the 4 th energy level at this time (too crowded).

5 th Row (cont) Indium goes back to putting electrons on the 5 th energy level, so it puts the 3 rd electron on the 5 th energy level…. To Xenon, which puts the 8 th electron on the 5 th energy level. At this point, the 5 th energy level is the valance, so even though it can hold 32 electrons, no more electrons can be on the 5 th energy level at this time. The 5 th energy level will not be full until the 7 th row!

6 th Row Represents that the 6 th energy level is valance. Cesium is putting the 1 st electron on the 6 th energy level; Barium is putting the 2 nd electron on the 6 th energy level (*6 th energy level is now valance). Remember that the 4 th energy level did not fill back on the 5 th row. (It only went to 18 electrons with Cadmium). At this point, electrons will go back to finish filling the 4 th energy level, starting with the 19 th electron. Lanthanum puts the 19 th electron on the 4 th energy level. Cerium puts the 20 th electron on the 4 th energy level…ect, to Ytterbium which puts the 32 nd and final electron on the 4 th energy level (which is now full).

6 th Row (cont) Beginning with Lutetium, electrons will now return to filling the 5 th energy, so Lutetium puts the 9 th electron on the 5 th energy level (since the 5 th is no longer the valance at this point, it can now hold more than 8 electrons.) Hafnium puts the 10 th electron on the 5 th energy level.. Ect… to Mercury,, which is putting the 18 th electron on the 5 th energy level. At this point, the 5 th energy level is NOT yet full, but the next electron will not go on the 5 th energy level at this time (too crowded). Thallium goes back to putting electrons on the 6 th energy level, so it puts the 3 rd electron on the 6 th energy level…. To Radon, which puts the 8 th electron on the 6 th energy level. At this point, the 6 th energy level is the valance, so even though it can hold 32 electrons, no more electrons can be on the 6 th energy level at this time.

6 th Row (cont) The 6 th energy does not finish filling (it’s impossible because the atoms are too unstable to have that many protons to balance the electrons necessary to fill the 6 th energy level).

7 th Row Represents that the 7 th energy level is valance. Francium is putting the 1 st electron on the 7 th energy level; Radium is putting the 2 nd electron on the 7 th energy level (*7 th energy level is now valance). Remember that the 5 th energy level did not fill back on the 6 th row. (It only went to 18 electrons with Mercury). At this point, electrons will go back to finish filling the 5 th energy level, starting with the 19 th electron. Actinium puts the 19 th electron on the 5 th energy level. Thorium puts the 20 th electron on the 5 th energy level…ect, to Nobelium which puts the 32 nd and final electron on the 5 th energy level (which is now full).

7 th Row (cont) Beginning with Lawrencium, electrons will now return to filling the 6 th energy, so Lawrencium puts the 9 th electron on the 6 th energy level (since the 6 th is no longer the valance at this point, it can now hold more than 8 electrons.) Rutherfordium puts the 10 th electron on the 6 th energy level.. Ect… but it doesn’t go to 18 (as far as we know) because the atoms become too unstable. The 7 th energy level does not have electrons in the 3 rd – 8 th Positions (atoms would be too unstable.) The 7 th energy level does not finish filling (again, atoms would become too large/unstable.)

If you are still confused… Go back and read all the notes again.. WITH YOUR PERIODIC TABLE. Each time the name of an element is mentioned, find that element, then read what electron and energy level it is filling. You have to go back and forth between the notes and the periodic table for this to make any kind of sense!