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 • Neutral Sodium has 11 protons (p+) and 11 electrons (e-) • First layer fills up with 2 electrons - 9 left over • Next layer fills up with 8 electrons - 1 left over • Last electron is all alone in the next layer
Electron Energy Levels: • 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 Configuration and Energy Levels: • Electrons can not exist between energy levels (shells). • They must jump from one level to the next. • 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.
Electrons become excited, and move to a higher energy level. Electron returns to Ground State Energy is given off as light. Electron at Ground State. Add energy in the form of heat.
Emission Spectrum • 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, • 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.
Red . Orange . Yellow . Green . Blue . Indigo . Violet Red Orange Yellow Green Blue Indigo Violet Long wavelength Less Energy Short wavelength Greater Energy
Flame Test • We will place samples of elements into a flame. • 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.
Flame Test • 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. • Different elements will have different flame colors because of their unique electrons. • This characteristic spectrum can be used to identify an element.