Notes #3: History of the Atom (Part 3) WCHS Chemistry
RUTHERFORD
WRONG! Correct :) NEILS BOHR (1919) Bohr Model of the Atom Electrons orbit around the nucleus like planets around the sun Each orbit is a different energy level: Farther from nucleus → greater energy Highest Energy WRONG! 4 3 2 1 Nucleus Correct :)
PROBLEMS!!! NEILS BOHR (1919) Bohr Model of the Atom Bohr’s model incorrectly said: E- are in specific places We can predict where orbits are
Discovered the neutron Must have a neutral “buffer” JAMES CHADWICK (1932) Discovered the neutron Must have a neutral “buffer”
BOHR’S MODEL VS. FLAME TESTS There are 2 states for an electron to be in: Ground State vs. Excited State Low energy e- picture ADD ENERGY e- gain energy to jump up to higher energy levels e- as close to nucleus as possible e- e- e- e- e- e- e- e-
BOHR’S MODEL VS. FLAME TESTS Then, they fall back down to their original orbit, releasing that energy as a photon of light. See light!! Photon We see photons of light. Different amounts of energy are different colors! Bohr’s model could predict these colors, but it only worked well for hydrogen -- why? B/c Hydrogen is so simple! → only 1 electron!
WHITE LIGHT Lowest Energy Highest Energy We see different colors of light due to different amounts of energy!
HYDROGEN EMISSION SPECTRUM You will see a “bar code” Every “bar” on the code is an electron releasing a photon when it falls back down from an excited state to ground state.
HELIUM EMISSION SPECTRUM
NITROGEN EMISSION SPECTRUM
NEON EMISSION SPECRUM