Download Unit 3: Electrons

Unit 3: Electrons
Overview- Honors Chemistry
Electrons
Energy
Spectroscopy
Wave properties &
equations, electromagnetic
spectrum, emission spectra,
and instrumental analysis
Modeling the Atom
Continued
Duality / wave-nature of
matter, wavefunctions,
quantum mechanics, and
the nature of science (NOS)
Electron Configurations
(Quantum Numbers)
Energy levels, sublevels,
orbitals, notation, rules, and
exceptions
Enduring Understandings
I.
II.
Energy is the capacity to do work.
 Energy (along with mass) is conserved.
 There is a trend in our universe toward lower energy.
Chemists use light, a form of energy, to study atoms and their electrons in a field of study known as spectroscopy.
 The electromagnetic spectrum classifies light based on wavelength/frequency/energy.
 Equations describe the relationship between wavelength, frequency, and energy:
c=λ∙ν
E=h∙ν
III.
Energy transitions that are whole-number multiples of Planck’s quantum are allowed, while others are not possible.
 Matter on the atomic scale is better described by quantum mechanics
 Since energy spacings are exceedingly small, macroscopic objects are described adequately by classical mechanics
(correspondence principle)
IV.
Atoms and molecules absorb and emit different wavelengths/frequencies of light based on their electronic structure (electron
arrangement).
 Line spectra are produced when electrons return from an excited state to their ground state after absorbing the exact energy of an
allowed transition.
 Bohr used Planck’s quantum theory and line spectra to develop a model of the atom containing quantized energy levels (orbits).
V.
VI.
VII.
VIII.
Light (Einstein) and electrons (de Broglie) have a dual nature: particle and wave.
 The nature of light/electrons depends on the technique one uses to study them.
Complex mathematical models are the basis for the quantum mechanical model of the atom.
 Schrödinger’s wavefunctions produc atomic orbitals that describe probable locations for finding electrons.
 Heisenberg’s uncertainty principle states that it is not possible to measure the momentum and position of a particle at the same
time with a great degree of accuracy/precision.
Electron configurations can be used as a qualitative method of describing the electron structure within atoms.
 Configurations for hydrogen-like atoms are governed by three rules:
Aufbau principle- electrons occupy orbitals of lowest energy first
Pauli exclusion principle- atomic orbitals can possess at most 2 electrons with opposite spins
Hund’s rule- electrons occupy orbitals in a way that maximizes same spin direction
The periodic table contains patterns in electron configurations and can be used as a tool to determine the energy order of atomic orbitals.