Electron configuration Electrons in Atoms

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Electrons zThe arrangement of electrons in an atom will determine the chemical and physical properties of that atom (or ion). zBecause of this it is important to know where those electrons are (or are most likely to be found)

Where do we find electrons? Electrons in atoms are arranged as LEVELS (n) SUBLEVELS (l) ORBITALS (m l ) Think of these as the electrons address.

Energy Level (n) This tells you how far the electron is from the nucleus, the higher the energy level the further from the nucleus zCurrently n can be 1 thru 7, because there are 7 periods on the periodic table

Energy Levels n = 1 n = 2 n = 3 n = 4

Sublevels zattempt to describe where the electrons are likely to be found ys, p, d, f ORBITALS zFound within the sublevels Each orbital can hold a maximum of 2 electrons

Types of Orbitals zThe most probable area to find these electrons takes on a shape zSo far, we have 4 shapes. They are named s, p, d, and f. zEach orbital has different “flavors” ys= 1 flavor yp = 3 flavors yd = 5 flavors yf = 7 flavors xEach “flavor” can hold a maximum of 2 electrons

s orbitals d orbitals Number of orbitals Number of electrons p orbitals f orbitals How many electrons can be in a sublevel? Remember: A maximum of two electrons can be placed in an orbital

Electron possible per energy level 2n 2 = the number of electrons possible in an energy level zEx: 3rd energy level, n=3 2(3) 2 = 18

Electron Configurations 2p 4 Energy Level Sublevel Number of electrons in the sublevel 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 … etc.

General Rules zPauli Exclusion Principle yEach orbital can hold TWO electrons with opposite spins.

General Rules zAufbau Principle yElectrons fill the lowest energy orbitals first. y“Lazy Tenant Rule”

Diagonal Rules s 3p 3d s 2p s 4p 4d 4f s 5p 5d 5f 5g? s 6p 6d 6f 6g? 6h? s 7p 7d 7f 7g? 7h? 7i? Steps: 1.Write the energy levels top to bottom. 2.Write the orbitals in s, p, d, f order. Write the same number of orbitals as the energy level. 3.Draw diagonal lines from the top right to the bottom left. 4.To get the correct order, follow the arrows! By this point, we are past the current periodic table so we can stop.

RIGHT WRONG General Rules zHund’s Rule yWithin a sublevel, place one e - per orbital before pairing them. y“Empty Bus Seat Rule”

O 8e - zOrbital Diagram zElectron Configuration 1s 2 2s 2 2p 4 Notation 1s 2s 2p

S 16e - Valence Electrons Core Electrons 1s 2 2s 2 2p 6 3s 2 3p 4 Notation zLonghand Configuration

LithiumLithium Group 1A Atomic number = 3 1s 2 2s 1 ---> 3 total electrons

CarbonCarbon Group 4A Atomic number = 6 1s 2 2s 2 2p 2 ---> 6 total electrons 6 total electrons

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