This document discusses quantum numbers, electron configurations, and periodic trends. It defines the principal, angular momentum, magnetic, and spin quantum numbers. The Pauli Exclusion Principle states that no two electrons can have the same four quantum numbers. Electrons fill orbitals based on the Aufbau principle and Hund's rule. Periodic trends include how the period and group number relate to energy levels and valence electrons. Exceptions to expected electron configurations involve gaining stability with full or half-full sublevels. Ions form to be isoelectronic with noble gases.

1. Quantum NumbersQuantum Numbers
1. Principal #1. Principal # →→
2. Ang. Mom. #2. Ang. Mom. # →→
3. Magnetic #3. Magnetic # →→
4. Spin #4. Spin # →→
energy levelenergy level
sublevel (s,p,d,f)sublevel (s,p,d,f)
orbitalorbital
electronelectron
Pauli Exclusion PrinciplePauli Exclusion Principle
– No two electrons in an atom can have theNo two electrons in an atom can have the
same 4 quantum numbers.same 4 quantum numbers.
– Each eEach e--
has a unique “address”:has a unique “address”:

2. General RulesGeneral Rules
Aufbau PrincipleAufbau Principle
– Electrons fill theElectrons fill the
lowest energylowest energy
orbitals first.orbitals first.
– ““Lazy StudentLazy Student
Rule”Rule”

3. General RulesGeneral Rules
The Diagonal RuleThe Diagonal Rule
2p
3p
4p
5p
6p
7p
3d
4d
5d
6d
4f
5f
2s
3s
4s
5s
6s
7s
1s
8s

4. WRONGRIGHT
General RulesGeneral Rules
Hund’s RuleHund’s Rule
– Within a sublevel, place one eWithin a sublevel, place one e--
per orbitalper orbital
before pairing them.before pairing them.
– ““Empty Bus Seat Rule”Empty Bus Seat Rule”

5. O
8e-
Orbital Diagram / Box & Arrow DiagramOrbital Diagram / Box & Arrow Diagram
Electron Configuration / SPDF NotationElectron Configuration / SPDF Notation
1s2
2s2
2p4
NotationNotation
1s 2s 2p

6. Shorthand ConfigurationShorthand Configuration
S 16e-
Valence ElectronsCore Electrons
S 16e-
[Ne] 3s2
3p4
1s2
2s2
2p6
3s2
3p4
NotationNotation
Longhand ConfigurationLonghand Configuration

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

8. Periodic PatternsPeriodic Patterns
Period #Period #
– energy level (subtract for d & f)energy level (subtract for d & f)
A/B Group #A/B Group #
– total # of valence etotal # of valence e--
Column within sublevel blockColumn within sublevel block
– # of e# of e--
in sublevelin sublevel

9. s-block1st Period
1s1
1st column
of s-block
Periodic PatternsPeriodic Patterns
Example -Example - HydrogenHydrogen

10. 1
2
3
4
5
6
7
Periodic PatternsPeriodic Patterns
Shorthand ConfigurationShorthand Configuration
– Core eCore e--
:: Go up one row and over to the NobleGo up one row and over to the Noble
Gas.Gas.
– Valence eValence e--
:: On the next row, fill in the # of eOn the next row, fill in the # of e--
in each sublevel.in each sublevel.

11. [Ar] 4s2
3d10
4p2
Periodic PatternsPeriodic Patterns
Example -Example - GermaniumGermanium

12. Full energy levelFull energy level
1
2
3
4
5
6
7
Full sublevel (s, p, d, f)Full sublevel (s, p, d, f)
Half-full sublevelHalf-full sublevel
StabilityStability

13. Electron Configuration ExceptionsElectron Configuration Exceptions
– CopperCopper
EXPECTEXPECT:: [Ar] 4s[Ar] 4s22
3d3d99
ACTUALLYACTUALLY:: [Ar] 4s[Ar] 4s11
3d3d1010
– Copper gainsCopper gains stabilitystability with a fullwith a full
d-sublevel.d-sublevel.
StabilityStability

14. Electron Configuration ExceptionsElectron Configuration Exceptions
– ChromiumChromium
EXPECTEXPECT:: [Ar] 4s[Ar] 4s22
3d3d44
ACTUALLYACTUALLY:: [Ar] 4s[Ar] 4s11
3d3d55
– Chromium gainsChromium gains stabilitystability with a half-full d-sublevel.with a half-full d-sublevel.
StabilityStability

15. StabilityStability
Ion FormationIon Formation
– Atoms gain or lose electrons to become more stable.Atoms gain or lose electrons to become more stable.
– Isoelectronic with the Noble Gases.Isoelectronic with the Noble Gases.

16. OO2-2-
10e10e--
[He] 2s[He] 2s22
2p2p66
StabilityStability
Ion Electron ConfigurationIon Electron Configuration
– Write the eWrite the e--
config for the closest Noble Gasconfig for the closest Noble Gas
– EXEX: Oxygen ion: Oxygen ion →→ OO2-2-
≡≡ NeNe