Quantum Model of the Atom

Electrons in Atoms

Quantum Mechanics

Radial Distribution CurveOrbital

Orbital (“electron cloud”)

Region in space where there is 90% probability of finding an e-

Quantum Numbers

UPPER LEVEL

Four Quantum Numbers:

Specify the “address” of each electron in an atom

Quantum Numbers

1. Principal Quantum Number ( n )

Energy level

Size of the orbital

n2 = # of orbitals in the energy level

Quantum Numbers

s p d f

2. Angular Momentum Quantum # ( l )

Energy sublevel

Shape of the orbital

Quantum Numbers

n = # of sublevels per level

n2 = # of orbitals per level

Sublevel sets: 1 s, 3 p, 5 d, 7 f

Quantum Numbers

3. Magnetic Quantum Number ( ml )

Orientation of orbital

Specifies the exact orbitalwithin each sublevel

C. Quantum Numbers

px py pz

C. Quantum Numbers

Orbitals combine to form a spherical shape.

2s

2pz2py

2px

Quantum Numbers

4. Spin Quantum Number ( ms )

Electron spin +½ or -½

An orbital can hold 2 electrons that spin in opposite directions.

Quantum Numbers

1. Principal # 2. Ang. Mom. # 3. Magnetic # 4. Spin #

energy level

sublevel (s,p,d,f)

orbital

electron

Pauli Exclusion Principle

No two electrons in an atom can have the same 4 quantum numbers.

Each e- has a unique “address”:

General Rules

Aufbau Principle

Electrons fill the lowest energy orbitals first.

“Lazy Student Rule”

General Rules

The Diagonal Rule

2p3p4p5p6p7p

3d4d5d6d

4f5f

2s3s4s5s6s7s

1s

8s

WRONGRIGHT

General Rules

Hund’s Rule

Within a sublevel, place one e- per orbital before pairing them.

“Empty Bus Seat Rule”

O

8e-

Orbital Diagram / Box & Arrow Diagram

Electron Configuration / SPDF Notation

1s2 2s2 2p4

Notation

1s 2s 2p

Shorthand Configuration

S 16e-

Valence Electrons

Core Electrons

S 16e- [Ne] 3s2 3p4

1s2 2s2 2p6 3s2 3p4

Notation

Longhand Configuration

© 1998 by Harcourt Brace & Company

sp

d (n-1)

f (n-2)

1234567

67

Periodic Patterns

Periodic Patterns

Period # energy level (subtract for d & f)

A/B Group # total # of valence e-

Column within sublevel block # of e- in sublevel

s-block

1st Period

1s11st column of s-block

Periodic Patterns

Example - Hydrogen

1

2

3

4

5

6

7

Periodic Patterns

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.

[Ar] 4s2 3d10 4p2

Periodic Patterns

Example - Germanium

Full energy level

1

2

3

4 5

6

7

Full sublevel (s, p, d, f)Half-full sublevel

Stability

Electron Configuration Exceptions

Copper

EXPECT: [Ar] 4s2 3d9

ACTUALLY: [Ar] 4s1 3d10

Copper gains stability with a full d-sublevel.

Stability

Electron Configuration Exceptions

Chromium

EXPECT: [Ar] 4s2 3d4

ACTUALLY: [Ar] 4s1 3d5

Chromium gains stability with a half-full d-sublevel.

Stability

Stability

Ion Formation Atoms gain or lose electrons to become more

stable. Isoelectronic with the Noble Gases.

O2- 10e- [He] 2s2 2p6

Stability

Ion Electron Configuration

Write the e- config for the closest Noble Gas

EX: Oxygen ion O2- Ne