Arrangement of Electrons in Atoms Chapter 4 Arrangement of Electrons in Atoms
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
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)
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) () J = (Js) (Hz) Planck’s constant: 6.626 X 10-34 Js
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
Ground state: lowest nrg state Excited state: higher potential nrg
--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
Line-Emission Spectrum excited state ENERGY IN PHOTON OUT ground state
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
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 A. Electrons as Waves Diffraction: bending of a wave as it passes by the edge of an object Interference: results when waves overlap
EVIDENCE: DIFFRACTION PATTERNS VISIBLE LIGHT ELECTRONS
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
Video #14(Quantum Mechanics: Schrod) Schrödinger Wave Equation (1926) finite # of solutions quantized energy levels defines probability of finding an e-
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 = 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
Radial Distribution Curve Orbital (“electron cloud”) Region in space where there is 90% probability of finding an e- Orbital Radial Distribution Curve
Specify the “address” of each electron in an atom 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
p s d f 2. Angular Momentum Quantum # ( l ) Energy sublevel Shape of the orbital f s d p
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 orbital within 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 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:
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
Noble gases: are inert complete octet --show ex----
Table 4-3 pg 110 1. Principal # energy level 2. Ang. Mom. # sublevel (s,p,d,f) 3. Magnetic # orbital 4. Spin # electron
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