Chm 11
Terms
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- Electromagnetic (EM) radiation
- Energy transmitted by wave propagation of electric and magnetic fields
- Wavelength
- Distance wave travels in one cycle
- Frequency
- Number of cycles per unit time
- Velocity
- Distance per unit time
- Diffraction
- Dispersion (separation) of different wavelengths of light by reflection from a grooved surface
- Diffraction: constructive interference
- waves interact in-phase (amplitude increase)
- Diffraction: destructive interference
- waves interact out of phase (amplitude reduction)
- Diffraction: grooved surface (grating)
- results in interference between reflected wavelenths
- Refraction
- dispersion of light as it passes through a different medium (material)
- Refraction: velocity of light
- reduced by interaction with atoms and molecules matter
- Refraction: degree of refraction
- dependent of frequency of light
- Spectrum
- band of different wavelenths from dispersed EM radiation
- continuous spectrum
- contains approximately all wavelengths in a given range
- discontinuous specrum
- contains small number of discrete wavelength
- Atomic line spectrum
- discontinuous spectrum produced by excited atoms
- atomic emission
- gas phase atoms emit light when thermally or electrically excited
- line spectra
- discrete wavelengths correspond to electrons changing orbits (photon emission)
- Balmer
- fit oberseved wavelengths (visible) of H-atom line spectrum to mathematical equation
- Plank
- atoms emit/absorb only discrete amounts (quanta) of energy
- Photoelectric effect
- ejection of electrons when photons strike a metal surface
- light intensity
- number of photons per unit time (no effect unless above threshold frequency)
- Bohr
- Developed model to explain line spectrum of the hydrogen atom
- atomic energy levels
- fixed orbits of electrons around the nucleus (discrete allowed states)
- photon absorbtion
- e- moves to higher orbit
- photon emission
- e- moves to lower orbit
- Why is the Bohr model limited and inaccurate
-
only predicts spectra for one-electron systems
electrons do NOT move in fixed orbits - Energy states of an ato (Bohr model)
-
ground state=lowest energy level
excited state=energy level higher than ground state - Z
- numlear charge (atomic #)
- n
- energy level (integer for allowed state)
- Photon energy
- difference in energy between state (consevation of energy)
- Quantum mechanics
- application of wave properties to matter
- Wave-particle duality
- light exhibits both wave and particle properties and behavior
- de Broglie
- matter exhibits both partible and wave properties
- Mater waves
- waves associated with material particles of nuclear or atomic dimensions
- Standing waves
- crests and troughs occur at fixes positions (amplitude at fixed endpoints)
- nodes
- points in wave with constant zero amplitude (no displacement during wave oscillation)
- wavefunction
- mathematical function describing wave motion of a particle
- schrodinger equation
- extracts physically relevant information from allowed wavefunctions
- principal quantum #(n)
-
describes average radial distance of electron from nucleus
n=positive, non zero integer - Orbital angular momentum quantum # (l)
- determines angular distribution fo orbital
- energy sublevel(subshell)
- subset of principal energy level
- sublevel notation
- n value followed by sublevel name
- Magnetic quantum # (ml)
- determines orientation of electron orbital
- # values for ml
- # electron orbitals within particular sublevel
- Orbital energies (one-electron system)
-
defined by principal quantum number (n)
sublevels=degenerate (same energy) within principal level for one-electron system - Electron charge density
- probability density of finding e- at a point
- probability density distribution
- three dimensional "shape" or orbital
- s orbital
- greatest electron density at the nucleus; spherical shape
- p orbital
- no electron density at the nucleus; non-spherical shape
- d orbital
- no electron density at nucleus; various (non-spherical) shapes
- orbital energies
- affected by charge interactions within atom
- nuclear charge (Z)
- positive charge of nucleus (attracts negative electrons)
- Electron shielding
- one electron shields another electron from the full nuclear charge
- effective nuclear charge
- nuclear charge actually experienced by electron
- Electron penetration
- ability of an electron to approach nucleus (depends on l)
- radial probability distribution
- probability of finding e- at a certain radius from nucleus
- orbital energies (multi-electron system)
-
sublevel energies altered by electron penetration and shielding
one electron system=no electon-electron relulsion--sublevel energies degenerate (same energy) - multi-electron system
- sublevel energies separated due to electron penetrarion and shielding
- Electron spin
- movement of electron on tis ezis generates magnetic field
- electron spin quantum number (ms)
- indicates direction of electron spin
- electron configuration
- designation of how electrons are distributed in orbitals
- orbital filling order
- in terms of increasing orbital energy
- pauli exclusion principle
- each electron must have a unique set of quantum numbers
- Hund's rule
- if degenerate orbitals are avaiable electron-electron repulsion is minimized
- Aufbau method
- distribute electrons to minimize energy
- periodic table
- indicates filling order in terms of increasing orbital energy
- principle quantum # (n)
- related to period (row) number
- abbreviated notation
- noble gas symbol used to represent core electrons
- superscripts
- indicate number of electrons in each orbital
- d-orbitals
- lower energy associated with half filled and filled sublevels