1. Isotope Formulae, Electron Configurations & Orbital Diagrams

2. Isotope Formulae Provide element’s symbol Mass number Atomic number
mass# = #p+ + #n
written as a superscript to the left
Atomic number
atomic# = #p+ or #e-
written as a subscript to the left

3. X C C Isotope Formulae Mass# Atomic# 12 6 13 6
Carbon has two naturally occurring isotopes:
carbon-12 and carbon-13 C 12 6 C 13 6

4. Isotope Formulae
Give the isotope formula for each of the
following: H 3 1
1. Hydrogen with 2 neutrons F 18 9
2. Fluorine with 9 neutrons U
235 92
3. Uranium with 143 neutrons

5. Valence Electron(s)
The electron(s) farthest from the nucleus or in the outermost energy level.

6. Aufbau Principle Comes from German word meaning “to build”
Electrons will occupy lower energy orbitals first

7. Pauli Exclusion Principle
An atomic orbital can hold at most two electrons.
If an atomic orbital holds two electrons, they must have opposite spins.

8. Hund’s Rule
When filling atomic orbitals of equal energy, place electrons with parallel spins in the orbitals first. Then, place the oppositely spinning electrons in to the orbitals.

9. Electron Configurations
Also describe where electrons live within an atom
It’s like a translation of quantum numbers.
They give the energy level, atomic orbital, and number of electrons residing in the orbital and energy level.

10. Electron Configurations
Energy level
May be any positive integer
Just like the principal quantum number

11. Electron Configurations
Atomic Orbital or Sublevel
Represented by letters: s, p, d, f
Translates azimuthal number and magnetic number
s is the same as l = 0
p is the same as l = 1
d is the same as l = 2
f is the same as l = 3

12. Electron Configurations
Number of Electrons
in either an atomic orbital or a sublevel
max of 2 in the s sublevel
max of 6 in the p sublevel
max of 10 in the d sublevel
max of 14 in the f sublevel

13. Electron Configurations
Use the periodic table to guide you in writing electron configurations.
Find the link between 2,6,10, and 14 and the periodic table.

14. Electron Configurations
Hydrogen
energy level
1s1
# of electrons
sublevel/orbital

15. Electron Configurations
Write the e- configurations of the next 9 elements (through Ne).
He…
1s2
Li…
1s22s1
Look at the sum
of the superscripts…
Be…
1s22s2 B…
1s22s22p1

16. Electron Configurations
1s22s22p2 N…
1s22s22p3 O…
1s22s22p4 F…
1s22s22p5
Ne…
1s22s22p6

17. Electron Configurations
Shorthand configurations are written by assuming that you can let the symbol of the noble gas preceding the valence electrons represent the e- configuration to that point.

18. Electron Configurations …shorthand
He…
1s2
Li…
[He]2s1
Be…
[He]2s2 B…
[He]2s22p1 C…
[He]2s22p2

19. Electron Configurations …shorthand
[He]2s22p3 O…
[He] 2s22p4 F…
[He] 2s22p5
Ne…
[He] 2s22p6

20. Electron Configurations …shorthand
Na…
[Ne]3s1
Si…
[Ne] 3s23p2
Cl…
[Ne] 3s23p5
Ar…
[Ne] 3s23p6

21. Electron Configurations …shorthand
Ca…
[Ar]4s2
Sc…
[Ar] 4s23d1
Mn…
[Ar] 4s23d5
Se…
[Ar] 4s23d104p4

22. Electron Configurations …shorthand
[Kr] 5s24d105p5
La…
[Xe] 6s25d1
Ce…
[Xe] 6s25d14f1
Hg…
[Xe] 6s24f145d10

23. Exceptional Electron Configurations…shorthand
Cr…
[Ar] 4s23d4
[Ar] 4s13d5
Cu…
[Ar] 4s23d9
[Ar] 4s13d10
Mo…
[Kr] 5s24d4
[Kr] 5s14d5
Ag…
[Kr] 5s24d9
[Kr] 5s14d10

24. Orbital Diagrams
Show the electron configuration while illustrating the Aufbau Principle, Pauli Exclusion Principle, and Hund’s Rule
Place energy on the y-axis
Use lines to represent orbitals
Use up and down arrows to indicate spin

25. Orbital Diagrams (template)
3px
3py
3pz 3s E
2px
2py
2pz 2s 1s

26. Orbital Diagram for H
3px
3py
3pz 3s E
2px
2py
2pz 2s 1s

27. Orbital Diagram for He
3px
3py
3pz 3s E
2px
2py
2pz 2s 1s

28. Orbital Diagram for Be
3px
3py
3pz 3s E
2px
2py
2pz 2s 1s

29. Orbital Diagram for C
3px
3py
3pz 3s E
2px
2py
2pz 2s 1s

30. Orbital Diagram for O
3px
3py
3pz 3s E
2px
2py
2pz 2s 1s

31. Orbital Diagram for P
3px
3py
3pz 3s E
2px
2py
2pz 2s 1s

32. Wrap-Up Write the electron configuration for nitrogen.
Write the orbital diagram for nitrogen.