CHM2041 Chapter 8 Atomic Structures Fully Composed & the Best Scouring Guide
Electromagnet Radiation - energy can be transformed between atoms and
... [Show More] molecules in the form of light or electromagnetic
dual nature of light - wave and particle
transverse wave - perpendicular oscillating electric and magnetic fields
wavelength (lambda) - distance traveled by wave in 1 complete oscillation; distance from the top (crest) of one wave to the top of the next wave; or successive troughs or nodes
all visible and invisible wavelengths are called - ultraviolet radiation
ROY G BIV Radiation - 380-750 nm; eyes detect this radiation
1 angstrom = - 1x10^-10 m = 1x10^-18 cm
speed of propagation, c - distance traveled by ray per unit time in vacuum; all electromagnetic radiation travel at same rate (speed of light)
= 2.998x10^8
Planck's Equation - -an object can gain or lose energy by absorbing or emitting radiant energy in quanta of specific frequency (v)
-E=hv=h(c/lambda)
-E= energy of a photon
-h= planck's constant= 6.626x10^-34 Jxs/photon
The Photoelectric Effect - -light can strike the surface of some metals causing electrons to be ejected (light: specific v or E)
-demonstrates the particle nature of light
Atomic line spectra and the Bohr atom - an emission spectrum is formed when an electric current passes through a gas in a vacuum tube (very low pressure) causing the gas to emit light
-sometimes called a bright light spectrum
Rydberg Equation - an empirical equation that predicts the wavelengths of the lines in the hydrogen spectrum
- 1/lambda= R(1/n(1)^2 - 1/n(2)^2)
-R= 1.097 x10^7 m^-1
-the n's refer to the numbers of the energy levels in the emission spectrum of hydrogen
Bohr model of atom - -energies of e are quantized: e occupy certain orbits of specific energies
-bohr's theory correctly explains the H emission spectrum and those of hydrogen-like ions (He+, Li2+, Be3+....etc.; 1e species)
-the theory fails for all other elements (treats electron as particle)
-the wave nature of the electron: deBroglie
Energy is absorbed.... - an e in an atom jumps from ground level (n=1) to upper levels (n>1)
-atom is now in an excited state
(absorption spectrum)
Energy is emitted.... - e jumps down from upper levels to lower levels; absorbed energy is then emitted as light; emission of photons
(emission spectrum)
Calculating Energy Difference, (Triangle)E, between 2 levels - (triangle)E= I E(final) - E(initial) I = R(H)(1/n(f)^2 - 1/n(i)^2)
-R(H)= 2.18x10^-18
Wave Nature of Electron - -wavelike properties of matter
-lambda= h/mv = h/p
-h: planck's constant
-m: mass of moving particle
-v: velocity of particle
p=mv: momentum
Uncertainty Principle - it is impossible to determine both the position (x) and the momentum (p) of an electron simultaneously
- e does not orbit the nucleus in defined paths (no orbits)
Basic Postulates of Quantum Theory - 1. Atoms and molecules exist in certain energy states. Atoms and molecules change energy states by absorbing or emitting enough energy to bring it to a new energy state (the quantum condition)
2. atoms or molecules absorb or emit radiation (light) to change their energies. The V and lambda of light emitted or absorbed are related to the energy change by: E= hv = hc/lambda
3. allowed energy states of atoms and molecules can be described by quantum numbers
- quantum numbers: solutions of the schrodinger, Heisenberg, and Dirac equations
Schrodinger's equation - H (wavelength: looks like a trident) = E (wavelength) [Show Less]