C. Johannesson IV. Electron Configuration (p , ) Ch. 4 - Electrons in Atoms

Diagonal Rule zThe diagonal rule is a memory device that helps you remember the order of the filling of the orbitals from lowest energy to highest energy zAufbau principle states that electrons fill from the lowest possible energy to the highest energy

Diagonal Rule ysysysys ysysysys 3p 3d ysysysys 2p ysysysys 4p 4d 4f ysysysys 5p 5d 5f 5g? ysysysys 6p 6d 6f 6g? 6h? ysysysys 7p 7d 7f 7g? 7h? 7i? ySteps: 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! yBy this point, we are past the current periodic table so we can stop.

Why are d and f orbitals always in lower energy levels? zd and f orbitals require LARGE amounts of energy zIt’s better (lower in energy) to skip a sublevel that requires a large amount of energy (d and f orbitals) for one in a higher level but lower energy This is the reason for the diagonal rule! BE SURE TO FOLLOW THE ARROWS IN ORDER!

C. Johannesson

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

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

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

C. Johannesson O 8e - zOrbital Diagram zElectron Configuration 1s 2 2s 2 2p 4 B. Notation 1s 2s 2p

Draw these orbital diagrams! zCarbon(C) zNitrogen (N)

C. Johannesson zShorthand Configuration S 16e - Valence Electrons Core Electrons S16e - [Ne] 3s 2 3p 4 1s 2 2s 2 2p 6 3s 2 3p 4 B. Notation zLonghand Configuration

C. Johannesson © 1998 by Harcourt Brace & Company s p d (n-1) f (n-2) C. Periodic Patterns

C. Johannesson C. Periodic Patterns zPeriod # yenergy level (subtract for d & f) zA/B Group # ytotal # of valence e - zColumn within sublevel block y# of e - in sublevel

C. Johannesson s-block1st Period 1s 1 1st column of s-block C. Periodic Patterns zExample - Hydrogen

Let’s Try It! zWrite the electron configuration for the following elements: H Li N Ne K Zn Pb

Let’s Try It! zWrite the electron configuration for the following elements: H1s 1 Li 1s 2 2s 1 N1s 2 2s 2 2p 3 Ne1s 2 2s 2 2p 6 K1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 Zn1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 Pb1s 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 5d 10 6p 2

C. Johannesson C. Periodic Patterns zShorthand Configuration yCore e - : Go up one row and over to the Noble Gas. yValence e - : On the next row, fill in the # of e - in each sublevel.

C. Johannesson [Ar]4s 2 3d 10 4p 2 C. Periodic Patterns zExample - Germanium

C. Johannesson zFull energy level zFull sublevel (s, p, d, f) zHalf-full sublevel D. Stability

C. Johannesson zElectron Configuration Exceptions yCopper EXPECT :[Ar] 4s 2 3d 9 ACTUALLY :[Ar] 4s 1 3d 10 yCopper gains stability with a full d-sublevel. D. Stability

C. Johannesson zElectron Configuration Exceptions yChromium EXPECT :[Ar] 4s 2 3d 4 ACTUALLY :[Ar] 4s 1 3d 5 yChromium gains stability with a half-full d-sublevel. D. Stability

C. Johannesson

Try These! zWrite the shorthand notation for: Cu W Au y[Ar] 4s 1 3d 10 y[Xe] 6s 1 4f 14 5d 5 y[Xe] 6s 1 4f 14 5d 10

C. Johannesson D. Stability zIon Formation yAtoms gain or lose electrons to become more stable. yIsoelectronic with the Noble Gases.

C. Johannesson O 2- 10e - [He] 2s 2 2p 6 D. Stability zIon Electron Configuration yWrite the e - config for the closest Noble Gas yEX: Oxygen ion  O 2-  Ne

Keep an Eye On Those Ions! zElectrons are lost or gained like they always are with ions… negative ions have gained electrons, positive ions have lost electrons zThe electrons that are lost or gained should be added/removed from the outermost energy level (not the highest orbital in energy!)

Keep an Eye On Those Ions! zTin Atom: [Kr] 5s 2 4d 10 5p 2 Sn +4 ion: [Kr] 4d 10 Sn +2 ion: [Kr] 5s 2 4d 10 Note that the electrons came out of the outermost energy level, not the highest energy orbital!

Keep an Eye On Those Ions! zBromine Atom: [Ar] 4s 2 3d 10 4p 5 Br - ion: [Ar] 4s 2 3d 10 4p 6 Note that the electrons went into the outermost energy level, not the highest energy orbital!

Try Some Ions! zWrite the longhand notation for these: F - Li + Mg +2 zWrite the shorthand notation for these: Br - Ba +2 Al +3 y1s 2 2s 2 2p 6 y1s 2 y1s 2 2s 2 2p 6  note this is the same as F - this is called isoelectronic y[Ar]4s2 3d10 4p6 y[Kr]5s2 4d10 5p6 y[He]2s2 2p6