III Electron StructureA Energy Levels

• Energy levels are distances from the nucleus where electrons can be found

– there are 7 energy levels » 1st is the lowest energy and closest to

nucleus» Each level holds a maximum number of

electrons

B Ground State and Excited State1. 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

C Electron Configuration– Explains where electrons exist

»Energy levels (n)»Sublevels»Orbitals

1. Energy levels (n)n = 1 holds 2 electronsn = 2 holds 8 electronsn = 3 holds 18 electronsn = 4 holds 32 electrons

2. Sublevels (l)-shapes of regions where electrons are found

»s»p»d»f

3. Orbitals (ml)-actual location of electrons

– s»contains 1 orbital = 2 electrons

– p»contains 3 orbitals = 6 electrons

– d»contains 5 orbitals =10 electrons

– 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

1s2s 2p3s 3p 3d4s 4p 4d 4f5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f

Lowest level

Highest level

Example• Write the electron configuration

for 16S– 16 protons.....16 electrons

• Electron configuration 1s22s22p63s23p4

• Electron configuration is 2-8-6

1s22s22p63s23p4

2-8-6

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:1. 11Na2. 6C3. 33As4. 17Cl5. 3Li6. 13Al7. 10Ne8. 35Br9. 18Ar10. 8O

• Na = 1s22s22p63s1

• C = 1s22s22p2

• As = 1s22s22p63s23p64s23d104p3

• Cl = 1s22s22p63s23p5

• Li = 1s22s1

• Al = 1s22s22p63s23p1

• Ne = 1s22s22p6

• Br = 1s22s22p63s23p64s23d104p5

• Ar = 1s22s22p63s23p6

• O = 1s22s22p4

• 1s22s22p63s23p4