Introductory Chemistry Fourth Edition Nivaldo J. Tro

1. Atom video
http://www.youtube.com/watch?v=x
qNSQ3OQMGI&feature=share

2. Basic Principle:
electrons occupy
lowest energy
levels available

4. 1
1s
value of energy level
sublevel
no. of
electrons
spdf NOTATION
for H, atomic number = 1
spdf Notation
Orbital Box Notation
Arrows show
electron spin
(+½ or -½)
ORBITAL BOX NOTATION
for He, atomic number = 2
1s
2
1s 
2 ways to write electron configurations

5. Example:
Determine the electron configuration and orbital
notation for the ground state neon atom.
An orbital can contain a maximum of 2 electrons,
and they must have the opposite “spin.”
Pauli exclusion principle

6. Rules for Filling Orbitals
Bottom-up
(Aufbau’s principle)
Fill orbitals singly before doubling up
(Hund’s Rule)
Paired electrons have opposite spin
(Pauli exclusion principle)
Basic Principle:
electrons occupy
lowest energy
levels available

7. Electron configuration for As

8. Hund’s Rule -
Write the ground state configuration and the
orbital diagram for oxygen in its ground state

9. Outer electron configuration for the elements

10. Identify examples of the following principles:
1) Aufbau 2) Hund’s rule 3) Pauli exclusion

11. Note: Not written according to Aufbau, but grouping according to n

12. Phosphorus
Symbol: P
Atomic Number: 15
Full Configuration: 1s22s22p63s23p3
Valence Configuration: 3s23p3
Shorthand Configuration: [Ne]3s23p3



  
  
        
1s 2s 2p 3s 3p
Box Notation

13. Shorthand notation practice
Examples
● Aluminum: 1s22s22p63s23p1
[Ne]3s23p1
● Calcium: 1s22s22p63s23p64s2
[Ar]4s2
● Nickel: 1s22s22p63s23p64s23d8
[Ar]4s23d8 {or [Ar]3d84s2}
● Iodine: [Kr]5s24d105p5 {or [Kr]4d105s25p5}
● Astatine (At): [Xe]6s24f145d106p5
{or [Xe]4f145d106s26p5}
[Noble Gas Core] + higher energy electrons

14. Valence e’s for “main group” elements

15. Electronic configuration of Br
1s2 2s22p6 3s23p63d10 4s24p5
[Ar] 3d104s24p5
[Ar] = “noble gas core”
[Ar]3d10 = “pseudo noble gas core”
(electrons that tend not to react)
Atom’s reactivity is determined by valence electrons
valence e’s in Br: 4s24p5
highest n electrons

16. Rule-of-thumb for valence electrons
Examples
● Sulfur: 1s22s22p63s23p4 or [Ne]3s23p4
valence electrons: 3s23p4
● Strontium: [Kr]5s2
valence electrons: 5s2
● Gallium: [Ar]4s23d104p1
valence electrons: 4s24p1
● Vanadium: [Ar]4s23d3
valence electrons: 4s2 or 3d34s2
Identify all electrons at the highest
principal quantum number (n)
Use on exams,
but recognize
limitations
Use Table 8.9
for online HW

17. Selenium’s valence electrons
Pseudo noble gas core includes:
 noble gas electron core
 d electrons (not very reactive)
Written for increasing energy:

18. Core and valence electrons in Germanium
Pseudo noble gas core includes:
 noble gas core
 d electrons
Written for increasing energy: