Energy levels and valence electrons

Electrons and Energy Levels

• Electrons are found in energy levels

Energy level Capacity

Level # 1 2 electrons

Level # 2 8 electrons

Level # 3 8 electrons

* In the first orbit, there are 2 electrons. * In the second orbit, there are 7 electrons. * In the third orbit, there are no electron.

The energy level diagram for Fluorine

Diagrams for Hydrogen and Carbon

Hydrogen Carbon

Valence electrons

• The electrons in the outermost energy level of an atom.

• The number of valence electrons vary from 1 to 8.

• These are the electrons that participate in chemical bonding.

Electron dot diagrams

• Only show VALENCE electrons– Element symbol goes in the middle– One dot for each valence electron around the

symbol

Know the group know the valence electrons

• Elements belonging in Group IA ( H, Li, Na, K ) 1 valence electron for the alkia metals

• Elements belonging in Group IIA ( Be, Mg, Ca ) 2 valence electrons for alkaline earth metals

• Elements belonging in Group IIIA (B, Al) 3 valence electrons for the boron family

• Elements belonging in Group IVA (C, Si) 4 valence electrons for the Carbon group

* Elements belonging in Group VA (eg - N, P) 5 valence electrons for elements belonging to Group VA).

* Elements belonging in Group VIA (eg - O, S) 6 valence electrons for elements belonging to Group VIA).

* Elements belonging in Group VIIA (eg - F, Cl) there are 7 valence electrons for elements belonging to Group VIIA).

* Elements belonging in Group VIIIA (eg - He, Ne, Ar) there are 8 valence electrons for elements belonging to Group VIIIA).

To draw Bohr Diagrams• Draw the nucleus as a solid circle.

• Put the number of protons (atomic number) in the nucleus with the number of neutrons (atomic mass – atomic number) under it.

• Place the number of electrons (same as protons) in orbits around the nucleus by drawing circles around the nucleus.

• Remember,

• 1st shell – 2 electrons,

• 2nd shell – 8 electrons,

• 3rd shell – 8 electrons

•  Extras into the 4th energy level

Lewis Dot Diagrams• Write the symbol of the atom you are drawing the electron dot diagram for in

the middle of your paper. This symbol represents the nucleus of the atom and each of the four sides represents an orbital where electrons are located.

• Locate the element you are drawing on the periodic table of elements. Find the number of electrons in one atom of the element. The number of electrons is the same as the element's atomic number.

• Find the number of valence electrons (electrons in the outermost shell of the element) you might have to draw the element or look at the pattern

• Place one dot around the element for each valence electron (no more than two one a side)

• Place the dots in a counterclockwise fashion around the edges of the symbol. No element should have more than 8 dots (valence electrons)