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

Pauli Exclusion Principle 1. Principal #  2. Azim (Ang. Mom.) #  3. Magnetic #  4. Spin #  energy level sublevel (s,p,d,f) orbital electron yNo two electrons in an atom can have the same 4 quantum numbers. yEach e - has a unique “address.”

A. General Rules zPauli Exclusion Principle yEach orbital can hold TWO electrons with opposite spins. ySpin is the only difference between these two electrons’ quantum states.

O 8e - zOrbital Diagram: shows all the electrons in an atom as arrows. yEach box is an orbital. yJoined orbitals are sublevels. B. Notation 1s 2s 2p  UP arrows have a m s of +1/2  DOWN arrows have a m s of -1/2

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

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

1s 1 Just one electron in the 1s sublevel. C. Electron Configuration zGives the energy state for ALL the electrons in an atom. zHydrogen’s configuration is simplest and shortest because H only contains one electron.

1s 2 C. Electron Configuration zGives the energy state for ALL the electrons in an atom. zLithium contains 3 electrons: y2 in the 1s (#1 & #2) y1 in the 2s (#3) 2s

1s 2 Sulfur’s last 4 electrons are in 3p. C. Electron Configuration zGives the energy state for all the electrons in an atom. zSulfur’s configuration needs to include ALL 16 of its electrons s 2 2p 6 3s 2 3p 4 All e-configs start at 1s. Powers should add up to atomic # ( =16)

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

C. Johannesson zShorthand (Noble Gas) Configuration S 16e - Valence Electrons Core Electrons (up to previous Noble) S16e - [Ne-10] 3s 2 3p 4 1s 2 2s 2 2p 6 3s 2 3p 4 B. Notation zLonghand Configuration

C. Johannesson C. Periodic Patterns zAufbau Principle: electrons always fill in order from lowest energy to highest energy. zAtomic numbers on the periodic table count electrons in the order they fill, so the order is always the same. Don’t forget where the f-block goes!

C. Periodic Patterns zAufbau Series: the order in which electrons fill energy levels & sublevels. 3p 6 4s 2 1s 2 2p 6 3s 2 4p 6 3d 10 2s 2 … 5p 6 6d 10 4d f 14 6s 2 5d 10 5s 2 7p 6 6p 6 7s 2 5f 14

C. Periodic Patterns  Orbital diagrams show the same information as electron configuration in a different way. The Aufbau Series still applies!

1s 2 C. Electron Configuration zExample – Nickel (Ni #28) Ni 1 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d = 28

C. Johannesson C. Periodic Patterns zShorthand Configuration yCore e - : Start with the noble gas from the previous period. yValence e - : On the next row, fill in the # of e - in each sublevel.

C. Johannesson [Ar-18] 4s 2 3d 10 4p 2 C. Periodic Patterns zExample - Germanium

C. Johannesson C. Periodic Patterns zPeriod # yenergy level (remember d & f don’t line up with s & p!) zA/B Group # ytotal # of valence e - zColumn within sublevel block y# of e - in sublevel

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

C. Johannesson s-block1st Period Hydrogen: 1s 1 1st column of s-block C. Periodic Patterns zElements in the same column have similar valence configurations.

s-block5th Period [Kr-36]5s 1 1st column of s-block C. Periodic Patterns zRubidium (Rb #37)

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 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