chapter 4 arrangement of electrons in atoms. i. the development of a new atomic model h...
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Chapter 4Chapter 4
Arrangement of Electrons in Atoms
Arrangement of Electrons in Atoms
I. The Development of a New Atomic Model
I. The Development of a New Atomic Model
Electromagnetic Radiation:
Electromagnetic Spectrum:
Electromagnetic Radiation:
Electromagnetic Spectrum:
Wavelength (): corresponding points on adjacent waves---Ex:
Frequency (): # of waves that pass a point in a specific time
c = () () ------inversely proportional
Wavelength (): corresponding points on adjacent waves---Ex:
Frequency (): # of waves that pass a point in a specific time
c = () () ------inversely proportional
c = () () ------inversely proportional
c : m/s : m, cm, nm : waves/second--Hertz (Hz)
c = () () ------inversely proportional
c : m/s : m, cm, nm : waves/second--Hertz (Hz)
Photoelectric Effect: emission of e- by certain metals when light shines on them
Photoelectric Effect: emission of e- by certain metals when light shines on them
Quantum: min quantity of nrg that can be lost or gained by an atom
E = (h) ()o J = (Js) (Hz)o Planck’s constant: 6.626 X 10-34 Js
Quantum: min quantity of nrg that can be lost or gained by an atom
E = (h) ()o J = (Js) (Hz)o Planck’s constant: 6.626 X 10-34 Js
• Einsteino dual wave-particle to describe light Photon: radiation with zero mass
carrying a quantum of nrgo packet of nrg emitted when an e- drops
nrg levels
• Einsteino dual wave-particle to describe light Photon: radiation with zero mass
carrying a quantum of nrgo packet of nrg emitted when an e- drops
nrg levels
Ground state: lowest nrg stateExcited state: higher potential nrg
Ground state: lowest nrg stateExcited state: higher potential nrg
--Bohr’s Model----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
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
Line-Emission Spectrum
ground state
excited state
ENERGY IN PHOTON OUT
Bohr Model
1
23
456 -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
Other Elements
Each element has a unique bright-line emission spectrum.
“Atomic Fingerprint”
Helium
Bohr’s calculations only worked for hydrogen! ----pg 97
II. The Quantum Model of the Atom
II. The Quantum Model of the Atom
A. Electrons as Waveso Diffraction: bending of a wave as it
passes by the edge of an objecto Interference: results when waves
overlap
A. Electrons as Waveso Diffraction: bending of a wave as it
passes by the edge of an objecto Interference: results when waves
overlap
EVIDENCE: DIFFRACTION PATTERNS
VISIBLE LIGHT ELECTRONS
Heisenberg Uncertainty Principle
Impossible to know both the velocity and
position of an electron at the same time
Schrödinger Wave Equation (1926)finite # of solutions quantized
energy levels
defines probability of finding an e-
Schrödinger Wave Equation (1926)finite # of solutions quantized
energy levels
defines probability of finding an e-
( ) ó3/2 Z∂
11s 0
−= eØ a
A. Atomic Orbitals and Quantum Numbers
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-o n = 1 -----occupies 1st nrg level
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-o n = 1 -----occupies 1st nrg level
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
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
Orbital (“electron cloud”)
Region in space where there is 90% probability of finding an e-
Orbital Radial Distribution Curve
Four Quantum Numbers:
Specify the “address” of each electron in an atom
UPPER LEVEL
1. Principal Quantum Number ( n )
Energy level
Size of the orbital
n2 = # of orbitals in the energy level
2. Angular Momentum Quantum # ( l )
Energy sublevel
Shape of the orbital
s p
d f
n = # of sublevels per level
n2 = # of orbitals per level
Sublevel sets: 1 s, 3 p, 5 d, 7 f
3. Magnetic Quantum Number ( ml )
Orientation of orbital
Specifies the exact orbitalwithin each sublevel
4. Spin Quantum Number ( ms )
Electron spin +½ or -½
An orbital can hold 2 electrons that spin in
opposite directions.
III. Electron ConfigurationIII. 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 orbito Ex:
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 orbito Ex:
Hund’s rule: orbital of equal nrg are occupied by 1 e-, before any is occupied by 2 e-’so Ex:
Orbital Notation: ex: pg 107
Electron Config Notation: pg 107Electron Dot diagram: ex
Hund’s rule: orbital of equal nrg are occupied by 1 e-, before any is occupied by 2 e-’so Ex:
Orbital Notation: ex: pg 107
Electron Config Notation: pg 107Electron Dot diagram: ex
Noble gases:are inertcomplete octet--show ex----
Noble gases:are inertcomplete octet--show ex----
Table 4-3 pg 1101. Principal # energy level2. Ang. Mom. # sublevel (s,p,d,f)3. Magnetic # orbital4. Spin # electron
Table 4-3 pg 1101. Principal # energy level2. Ang. Mom. # sublevel (s,p,d,f)3. Magnetic # orbital4. Spin # electron
Feeling overwhelmed?Feeling overwhelmed?