1) Electrons in atoms occupy different energy levels rather than following classical orbital models. Higher energy levels are farther from the nucleus. 2) Energy levels are divided into sublevels which have different shapes designated by letters. Electrons fill these sublevels according to specific rules. 3) The aufbau principle and Pauli exclusion principle govern how electrons fill atomic orbitals based on energy and allowing no more than two electrons of opposite spin per orbital. Hund's rule favors occupying each orbital in a sublevel singly before pairing electrons.

1. Electron Energy Level Notes

2. Electron Energy Level Notes
• Electrons do not travel around the nucleus
of an atom in orbits
• They are found in energy levels at different
distances away from the nucleus. (kind of like
shells or layers).

3. The Quantum Mechanical Model of the Atom (cont.)
The wave function predicts a three-dimensional region around the
nucleus called the atomic orbital.

4. Hydrogen Atomic Orbitals
Principal quantum number (n) indicates the relative size and energy of
atomic orbitals.
n specifies the atom’s major energy levels, called the principal energy
levels.
Electrons cannot exist between energy levels (just like the rungs of a ladder).

5. Electron Energy Level Notes
• Energy levels are broken up into sublevels:
• There are at least 4 possible types of
sublevels—given labels: s, p, d, or f
•

6. Hydrogen Atomic Orbitals (cont.)
Energy sublevels are contained within the principal energy levels.
1 = 1sublevel
,s
2 = 2sublevel
,sp
3 = 3sublevel
,spd
4 = 4sublevel
,spdf

8. Electron Energy Level Notes
• Only a certain number of electrons may
exist in an energy level, but the number
varies. It can be determined by:
• # of electrons in level = 2 x (# of energy level)2
• Therefore:
• energy level 1 = 2 (1)2 = 2
• energy level 2 = 2 (2)2 = 8
• energy level 3 = 18
• energy level 4 = 32
• etc...

9. Electron Energy Level Notes
• In each energy level, electrons fill sublevels in a
certain order
• Level 1:
• only has one s sublevel (a spherical shape)
• 2 electrons may fit in this sublevel--each one has
an opposite “spin”, allowing them to take up the
same space
• Pauli exclusion principle—no more than 2
electrons may be found in the same orbital
(“orbital” means a particular location)

10. s-Orbital Image

11. Electron Energy Level Notes
• Level 2:
• has two sublevels: s and p
• 2 electrons in s
• there are 3 different p orbitals, and may hold 2
electrons each—6 total. (look at shape on p. 154--
imagine how they can fit together)
• total of 8 overall in Level 2

12. p-Orbital Image

13. Electron Energy Level Notes
• Level 3:
• has 3 sublevels: s, p, and d
• 2 electrons in s
• 6 electrons in p
• there are 5 different d orbitals, and 2 electrons
can fit in each—total of 10. (look at picture of d
orbitals, imagine how they can fit together)
• total of 18

14. d-orbital notes

15. Hydrogen Atomic Orbitals (cont.)
Each energy sublevel relates to orbitals of different shape.

16. Image of orbitals

17. Electron Energy Level Notes
• Level 4:
• has 4 sublevels: s, p, d , and f
• 2 electrons in s
• 6 electrons in p
• 10 electrons in d
• 14 electrons in f (7 different orbitals for f)
• total of 32

18. Hydrogen Atomic Orbitals (cont.)

19. Electron Energy Level Notes
• The order that electrons fill up orbitals
does not follow the logical order of all 1’s,
then all 2’s, then all 3’s, etc.
• They follow the order found based on
certain rules.

21. • ATOMIC # = #p+ = #e-

22. Order of Orbitals

23. Electron Energy Level Notes
• An easy way to remember this is to use
the periodic table--it is arranged to show
how these orbitals are filled.

24. Order of Orbitals—Periodic Table

25. Ground-State Electron Configuration
The arrangement of electrons in the atom is
called the electron configuration.
The aufbau principle states that each electron
occupies the lowest energy orbital available.

26. Ground-State Electron Configuration (cont.)
The Pauli exclusion principle states that a
maximum of two electrons can occupy a
single orbital, but only if the electrons have
opposite spins.
Hund’s rule states that single
electrons with the same spin
must occupy each equal-energy
orbital before additional
electrons with opposite spins
can occupy the same energy
level orbitals.

27. Electron Energy Level Notes
• Hund’s rule is used for filling orbitals with
electrons. It states that only one electron
will be put in each orbital of a sublevel until
all of them are filled, and after that, they
may be paired up until the sublevel is full.

28. Section 5-3
Ground-State Electron Configuration (cont.)

29. 3py 3pz

30. Section 5-3
Ground-State Electron Configuration (cont.)
Noble gas notation uses noble gas symbols in brackets to shorten
inner electron configurations of other elements.

31. Section 5-3
Ground-State Electron Configuration (cont.)
The electron configurations (for chromium, copper,
and several other elements) reflect the
increased stability of half-filled and filled sets of
s and d orbitals.

32. Section 5-3
Valence Electrons
Valence electrons are defined as electrons in the atom’s outermost
orbitals—those associated with the atom’s highest principal energy
level.
Electron-dot structure consists of the element’s symbol representing the
nucleus, surrounded by dots representing the element’s valence
electrons.

33. Section 5-3
Valence Electrons (cont.)