TEMA PARA LA MATERIA DE QUÍMICA...t/t

1. Electrons
QBA Miguel A. Castro Ramírez

2. Models of the Atom
Red Book: Section 5.1
Blue Book:13.1

3. Rutherford’s Failure
Rutherford’s model
could not describe
behavior of atoms
Think About It:
Why do certain
atoms react
while others
don’t? Why do
some fireworks
glow red and
others green?

4. Bohr’s Atom
Hypothesis: each
electron exists in a
certain “orbit” or
“energy level”
Electrons can never
exist in between
Higher energy levels
are further from the
nucleus

5. Quanta
A quantum (pl. quanta) is the amount of energy
required for an electron to move up an energy
level

6. Quantum Mechanical Model
Also called “electron
cloud model”
Mathematically-based

7. Quantum Mechanical Model
Determines allowed
electron energies and
how likely it is to find
an electron in various
locations around the
nucleus
Dense cloud = high
probability

8. Atomic Orbitals
 Region of space in
which there is a high
probability of finding
an electron
Why It’s Important:
The exact location
of each electron
controls the atom’s
properties!

9. “Address” of Electron
Each electron will be found
 On a PRINCIPAL ENERGY LEVEL
 In one of several SUBLEVELS
 On an ORBITAL

10. Principal Quantum Numbers
Each energy level is
assigned a principal
quantum energy
number, n
n can be 1, 2, 3, or 4,
etc…

11. Sublevels
 Each principal energy level
has specific sublevels
where an electron can be
found
 # of sublevels corresponds
to principal quantum
number
 Level 1 has 1 sublevel
 Level 2 has 2 sublevels…

12. Sublevels
Sublevels are given
letter designations
s
p
d
f

13. The orbital names (s,
Why s, p, p, d, f, g, h,...) are
d, and f? derived from the
characteristics of their
spectroscopic lines:
sharp, principal, diffuse
and fundamental, the
rest being named in
alphabetical order. For
mnemonic reasons,
some call them
spherical & peripheral.

14. Atomic Orbitals
s sublevel – 1 orbitals
p sublevel – 3
d sublevel – 5
f sublevel – 7

15. Atomic Orbitals
Each orbital can
hold one pair of
electrons
Each member of
the pair has an
opposite spin

16. How many total
electrons in each?

17. 1 Principal Energy Level
st
• 1 sublevel (s)
• 2 electrons in s orbital
• 2 total

18. 2 Principal Energy Level
nd
• 2 sublevels (s and p)
• 2 electrons in s orbital
• 6 electrons in p orbitals
• 8 total (10 combined with 1st)

19. 3 Principal Energy Level
rd
• 3 sublevels (s, p and d)
• 2 electrons in s orbital
• 6 electrons in p orbitals
• 10 electrons in d orbitals
• 18 total (28 combined with 1st and 2nd)

20. 4 Principal Energy Level
th
• 4 sublevels (s, p, d and f)
• 2 electrons in s orbital
• 6 electrons in p orbitals
• 10 electrons in d orbitals
• 14 electrons in f orbitals
• 32 total (50 combined with 1st, 2nd, and 3rd)

21. Electron Arrangement
Blue Book: 13.2
Red Book: 5.2

22. Electron Configuration
Way that
electrons are
arranged in
various orbitals
Arrangement
governed by
three rules

23. Aufbau Principle
Electrons first
occupy orbitals of
lowest energy
Sublevels from some
principal energy
levels overlap others

24. Aufbau Diagrams
Display the order in
which orbitals are filled
(to achieve the most
stable configuration)

25. Aufbau Principle

27. Pauli Exclusion Principle
Each orbital holds, at most, two electrons.
Two occupy the same orbital, two
electrons must have opposite spins.
This is written or

28. Hund’s Rule
In each sublevel, one
electron enters each
orbital until each has
one with the same spin
direction
Not until all orbitals
have one electron can
any have two

29. Orbital Filling Diagrams
Show
which
orbitals are
filled by
electrons

30. Writing Electron
Configurations

31. Electron Configurations
Sublevels are filled in the
following order:
1s, 2s, 2p, 3s, 3p,
4s, 3d, 4p, 5s

32. Electron Configurations
Contain 3 items:
Number represents energy level
Letter represents sublevel
Superscript represents number of electrons
1s 2

33. Electron Configurations
Additional segments needed for each
sublevel
1s 2s 2 2

34. Electron Configurations
1s 2s 2p2 2 6

35. Electron Configurations
of Specific Elements
In a neutral element, the number of electrons is
equal to the number of protons.

36. Electron Configurations
Hydrogen Silicon
Oxygen Calcium
Neon
Superscripts add up
to the total number
of electrons!