Electron Configuration Electrons in Atoms Electron Configuration

Energy levels, sublevels and orbitals (cloud or shell) Sublevels Orbitals Number of electrons 1 s 1 s orbital 2 s, p 3 p orbitals 8 3 s, p, d 5 d orbitals 18 4, 5, 6, 7 s, p, d, f 7 f orbitals 32

s orbitals 3s 2s 1s

Three p Orbitals px pz py

A. General Rules Pauli Exclusion Principle Each orbital can hold TWO electrons with opposite spins.

A. General Rules Aufbau Principle Electrons fill the lowest energy orbitals first.

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

1s2 2s2 2p4 O B. Notation 1s 2s 2p 8e- Orbital Diagram Electron Configuration 1s2 2s2 2p4

S 16e- 1s2 2s2 2p6 3s2 3p4 S 16e- [Ne] 3s2 3p4 B. Notation Longhand Configuration S 16e- 1s2 2s2 2p6 3s2 3p4 Core Electrons Valence Electrons Shorthand Configuration S 16e- [Ne] 3s2 3p4

C. Periodic Patterns s p d (n-1) f (n-2) 1 2 3 4 5 6 7 6 7 © 1998 by Harcourt Brace & Company

C. Periodic Patterns Period # (Row) indicates the highest energy level (subtract for d & f) Group # (column) Indicates the total # of valence e- Column within sublevel block # of e- in sublevel

1s1 C. Periodic Patterns 1st column of s-block 1st Period s-block Example - Hydrogen 1s1 1st column of s-block 1st Period s-block

C. Periodic Patterns p s d (n-1) f (n-2) Shorthand Configuration Core e-: Go up one row and over to the Noble Gas. Valence e-: On the next row, fill in the # of e- in each sublevel. s d (n-1) f (n-2) p

C. Periodic Patterns Example - Germanium [Ar] 4s2 3d10 4p2

D. Stability Full energy level Full sublevel (s, p, d, f) Half-full sublevel

D. Stability Electron Configuration Exceptions Copper EXPECT: [Ar] 4s2 3d9 ACTUALLY: [Ar] 4s1 3d10 Copper gains stability with a full d-sublevel.

D. Stability Electron Configuration Exceptions Chromium EXPECT: [Ar] 4s2 3d4 ACTUALLY: [Ar] 4s1 3d5 Chromium gains stability with a half-full d-sublevel.

D. Stability 1+ 2+ 3+ NA 3- 2- 1- Ion Formation Atoms gain or lose electrons to become more stable. Isoelectronic with Noble Gases. 1+ 2+ 3+ NA 3- 2- 1-

D. Stability Ion Electron Configuration Find the Noble Gas with the same number of electrons and write its symbol in brackets EX: Oxygen ion  O2- = 10 electrons = [ Ne ] Ex: Potassium ion  K+ = 18 electrons = [Ar]

Line Emission Spectrum The lowest energy state of an atom is called the ground state A state in which an atom has a higher potential energy than the ground state is called an excited state When an excited atom returns to the ground state, it gives off energy, usually in the form of light

Line Emission Spectrum When this light is shined through a prism, it is separated into a series of specific frequencies of light The bands of light are known as the line emission spectrum for the element Line emission spectrum for hydrogen

Photoelectric Effect The emission of electrons from a metal when light shines on the metal only occurs if the photons in the light have a certain minimum frequency (energy) Different metals require different minimum frequencies