1. Arrangement of Electrons in Atoms
Chapter 4
Arrangement of Electrons in Atoms

2. I. The Development of a New Atomic Model
Electromagnetic Radiation:
“radiant energy” form of nrg that has wave characteristics and can travel through a vacuum “light”
Electromagnetic Spectrum:
Distribution among various wavelengths of the radiant nrg emitted or absorbed by an object

3. Wavelength (): corresponding points on adjacent waves---Ex:
Frequency (): # of waves that pass a point in a specific time
c = () () inversely proportional

4. c = () () ------inversely proportional
c : m/s
 : m, cm, nm
 : waves/second--Hertz (Hz)

5. Photoelectric Effect: emission of e- by certain metals when light shines on them

6. Quantum: min quantity of nrg that can be lost or gained by an atom
E = (h) ()
J = (Js) (Hz)
Planck’s constant: X Js

7. Video #15 (wave function and wave particle)
Einstein
dual wave-particle to describe light
Photon: radiation with zero mass carrying a quantum of nrg
packet of nrg emitted when an e- drops nrg levels

8. Ground state:
lowest nrg state
Excited state:
higher potential nrg

9. --Bohr’s Model--
e- exist only in orbits with specific amounts of energy called energy levels
Therefore…
e- can only gain or lose certain amounts of energy
only certain photons are produced

10. Line-Emission Spectrum
excited state
ENERGY IN
PHOTON OUT
ground state

11. Bohr Model -Energy of photon depends on the difference in energy
levels
-Bohr’s calculated
energies matched
the IR, visible, and
UV lines for the H
atom 6 5 4 3 2 1

12. Other Elements
Each element has a unique bright-line emission spectrum.
“Atomic Fingerprint”
Helium
Bohr’s calculations only worked for hydrogen! ----pg 97

13. II. The Quantum Model of the Atom
A. Electrons as Waves
Diffraction: bending of a wave as it passes by the edge of an object
Interference: results when waves overlap

14. EVIDENCE: DIFFRACTION PATTERNS
VISIBLE LIGHT
ELECTRONS

15. Video # 13(What is the Heisenberg Uncert)
Heisenberg Uncertainty Principle
Impossible to know both the velocity and
position of an electron at the same time

16. Video #14(Quantum Mechanics: Schrod)
Schrödinger Wave Equation (1926)
finite # of solutions  quantized energy levels
defines probability of finding an e-

17. A. Atomic Orbitals and Quantum Numbers
Orbital: probable location of an e-
Quantum #: properties of atomic orbitals and properties of e-’s in orbitals
Principal quantum #: (n), indicates main nrg level occupied by the e-
n = occupies 1st nrg level

18. Angular momentum quantum #: (l), indicates shape of orbital
Magnetic quantum #: (m), orientation of an orbital
Spin quantum #: which spin state (+)(-)
***See table 4-2 pg 104

19. Radial Distribution Curve
Orbital (“electron cloud”)
Region in space where there is 90% probability of finding an e-
Orbital
Radial Distribution Curve

20. Specify the “address” of each electron in an atom
Four Quantum Numbers:
Specify the “address” of each electron in an atom
UPPER LEVEL

21. 1. Principal Quantum Number ( n )
Energy level
Size of the orbital
n2 = # of orbitals in the energy level

22. p s d f 2. Angular Momentum Quantum # ( l ) Energy sublevel
Shape of the orbital f s d p

23. n = # of sublevels per level
n2 = # of orbitals per level
Sublevel sets: 1 s, 3 p, 5 d, 7 f

24. 3. Magnetic Quantum Number ( ml )
Orientation of orbital
Specifies the exact orbital within each sublevel

25. 4. Spin Quantum Number ( ms )
Electron spin  +½ or -½
An orbital can hold 2 electrons that spin in
opposite directions.

26. III. Electron Configuration
Aufbau principle:
lowest nrg orbits fill first
Pauli exclusion principle:
no 2 e-’s can have the same 4 quantum #’s. This is where spin allows 2 e-’s to be in the same orbit
Ex: 

27. Electron Config Notation: pg 107 Electron Dot diagram: ex
Hund’s rule:
orbital of equal nrg are occupied by 1 e-, before any is occupied by 2 e-’s
Ex:   
Orbital Notation:
ex: pg 107
Electron Config Notation: pg 107
Electron Dot diagram: ex

28. Noble gases:
are inert
complete octet
--show ex----

29. Table 4-3 pg 110 1. Principal #  energy level
2. Ang. Mom. # sublevel (s,p,d,f)
3. Magnetic #  orbital
4. Spin #  electron

30. Feeling overwhelmed?