Quantum Rules

Degenerate orbitals

Orbitals of equal energy

Valence electrons

Electrons in highest principal energy level;
These are the electrons that govern chemistry.

Core electrons

Inner-shell electrons

Noble-gas notation

Uses noble gas symbol to represent core electrons

4s is lower energy than 3d (for neutral atoms)

4s fills before 3d because

Scandium

Element that begins filling the 3d subshell

5

Number of d orbitals

10

Maximum electrons in d subshell

7

Number of f orbitals

14

Maximum electrons in f subshell

Chromium and Copper

Two elements that are the exception to the Aufbau’s principle

Half-filled and filled d subshells have extra stability.

Why are Chromium and Copper are exceptions to the Aufbau principle

valence electron count

Elements in same group have same...

same valence electrons

Chemical similarity in a group comes from…

chemical reactivity

Valence electrons determine what?

Last electron enters s or p orbital

Main-group elements

Transition elements

Last electron enters d orbital

Inner transition elements

Last electron enters f orbital

Lanthanides

4f filling series

Actinides

5f filling series

Cation

Positive ion formed by losing electrons.

Anion

Negative ion formed by gaining electrons.

Highest n shell first

Main-group cations lose electrons from...

ns before (n−1)d

Transition metals lose electrons from...

ns before (n−1)d

Transition metals lose electrons from

4s

What fills first: 4s or 3d?

Single electrons first (Hund’s Rule)

What fills first in degenerate orbitals?

s electrons

What leaves first in transition-metal ions?

d

Which subshell has 10 electrons?

f

Which subshell has 14 electrons?

s = 2, p = 6, d = 10, f = 14

Capacities for each shell

s =1, p = 3, d = 5, f = 7

Orbital count for each shell

Aufbau principle

Lowest energy fills first

Hund principle

Fill singly before pairing.

Pauli

Max two electrons per orbital, opposite spins