III Electron Structure AEnergy Levels Energy levels are distances from the nucleus where electrons can be found –there are 7 energy levels »1 st is the lowest energy and closest to nucleus »Each level holds a maximum number of electrons

BGround State and Excited State 1.Ground State –Electrons are located in the lowest possible levels »Low energy—stable structure 2.Excited State –Electrons are located in higher levels »High energy—unstable structure

3.Emission Spectra –When an atom in the ground state absorbs energy, electrons get excited »These excited electrons, “jump” to a higher energy level [excited state] »When electrons return to ground state, they release energy in the form of light »Light pattern is unique for each element »Color is related to each electron transition

These spectral lines led to the discovery of how electrons were arranged in an atom CElectron Configuration –Explains where electrons exist »Energy levels (n) »Sublevels »Orbitals 1.Energy levels (n) n = 1 holds 2 electrons n = 2 holds 8 electrons n = 3 holds 18 electrons n = 4 holds 32 electrons

2. Sublevels ( l ) -shapes of regions where electrons are found »s»s »p»p »d»d »f»f

3. Orbitals ( ml ) -actual location of electrons –s–s »contains 1 orbital = 2 electrons –p–p »contains 3 orbitals = 6 electrons –d–d »contains 5 orbitals =10 electrons –f–f »contains 7 orbitals = 14 electrons

4. Writing electron configurations each orbital holds 2 electrons occupy then fill the lowest sublevel move to the next sublevel add electrons until all are used 1s 2s2p 3s3p3d 4s4p4d4f 5s5p5d5f 6s6p6d6f 7s7p7d7f Lowest level Highest level

Example Write the electron configuration for 16 S –16 protons electrons Electron configuration 1s 2 2s 2 2p 6 3s 2 3p 4 Electron configuration is 2-8-6

1s 2 2s 2 2p 6 3s 2 3p How many electrons in sulfur? 16 How many energy levels are used? 3 How many energy levels are filled? 2 How many sublevels are present? 5 How many sublevels are filled? 4

Write the electron structure for: Na 2. 6 C As Cl 5. 3 Li Al Ne Br Ar O

Na = 1s 2 2s 2 2p 6 3s 1 C = 1s 2 2s 2 2p 2 As = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 3 Cl = 1s 2 2s 2 2p 6 3s 2 3p 5 Li = 1s 2 2s 1 Al = 1s 2 2s 2 2p 6 3s 2 3p 1 Ne = 1s 2 2s 2 2p 6 Br = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 5 Ar = 1s 2 2s 2 2p 6 3s 2 3p 6 O = 1s 2 2s 2 2p 4 1s 2 2s 2 2p 6 3s 2 3p 4