Electron Configuration and Energy Levels: Ground state: All the electrons in an atom have the lowest possible energies Most stable electron configuration

Example: Sodium (Na) Pictures show all the electrons in a sodium atom Pictures show all the electrons in a sodium atom Neutral Sodium has 11 protons (p+) and 11 electrons (e-) Neutral Sodium has 11 protons (p+) and 11 electrons (e-) First layer fills up with 2 electrons - 9 left over First layer fills up with 2 electrons - 9 left over Next layer fills up with 8 electrons - 1 left over Next layer fills up with 8 electrons - 1 left over Last electron is all alone in the next layer Last electron is all alone in the next layer

All of the Electron Shells

Analogy: staircase. Can stand on a stair, not between stairs. It takes energy to raise from a lower stair to a higher stair. In the same way, electrons can be in lower or higher energy level but not in between. Electron Energy Levels:

Electrons can not exist between energy levels (shells). Electrons can not exist between energy levels (shells). They must jump from one level to the next. They must jump from one level to the next. Energy must be added to atom for electron to jump to higher energy level. Energy must be added to atom for electron to jump to higher energy level. When electron falls back to it’s original state, energy is released as specific wavelength of light. When electron falls back to it’s original state, energy is released as specific wavelength of light. Electron Configuration and Energy Levels:

Electron at Ground State. Add energy in the form of heat. Electrons become excited, and move to a higher energy level. Electron returns to Ground State Energy is given off as light.

Emission Spectrum Each element has different “energy staircase”, i.e. unique series of electron energy steps. Each element has different “energy staircase”, i.e. unique series of electron energy steps. To move between steps, electrons absorb or emit specific amounts of energy, To move between steps, electrons absorb or emit specific amounts of energy, Amount of energy corresponds to specific wavelengths (colors) of light. Amount of energy corresponds to specific wavelengths (colors) of light. Emission spectrum: unique series of energy differences (i.e. colors) between steps allows identification of elements by light energy they emit. Emission spectrum: unique series of energy differences (i.e. colors) between steps allows identification of elements by light energy they emit.

Red. Orange. Yellow. Green. Blue. Indigo. Violet Long wavelength Short wavelength Less Energy Greater Energy Red Orange Yellow Green Blue Indigo Violet

Flame Test We will place samples of elements into a flame. We will place samples of elements into a flame. This will add energy to the atom in the form of heat. This will add energy to the atom in the form of heat. The electrons will them become excited, and jump to a higher energy level. The electrons will them become excited, and jump to a higher energy level.

Flame Test Then the electrons will return to their original ground state. Then the electrons will return to their original ground state. As they return to a lower energy level, the energy will be given off in the form of light. As they return to a lower energy level, the energy will be given off in the form of light. Different elements will have different flame colors because of their unique electrons. Different elements will have different flame colors because of their unique electrons. This characteristic spectrum can be used to identify an element. This characteristic spectrum can be used to identify an element.