making estimates

Lecture IV: Atoms & Molecules (Ch. 6)

Take-home points on atoms and molecules:

  1. Atoms and Molecules exist -- subnanometer scale.
  2. Molecules are bound atoms.
  3. Energy can be extracted from molecules (tomorrow).

Scanning tunneling microscope sees atoms.

[1986 Nobel Prize: Binnig and Rohrer]
Current flow depends on tip-atom distance. Picture contrast is measure of current flow.
7 x 7 Si

stm diagram

Forming a molecule on a surface

FeCO_2 forming Ag (silver) surface with
absorbed Fe (iron) atom
and CO (carbon-monoxide).
(A) CO desorbs from surface
and binds to tip
(B) tip with CO moves
toward Fe on surface
(C) tip detaches CO that
moves to surface;
(D) single Fe-CO bond forms.

STM Pictures of Molecular Formation

FeCO_2 (A) Five Fe atoms and four CO molecules on Ag surface.
(B) formation of Fe-CO shown in whole figure above.
(C) Another Fe-CO formed.
(D) Second CO moved to Fe-CO to form Fe(CO)2.

Representations of Molecules

oxygen molecule Oxygen molecule: what is it?
CO_2 Carbon dioxide
NO_2 Nitrogen dioxide

More Representations of Molecules

ethane Ethane
and oxygen forming water Chemist view of hydrogen and oxygen forming wather.

Stick figures for larger molecules

methane stick
figure ethane stick figure
propane stick
figure butane stick figure

Combustion Example

propane combustion
Propane combusting with oxygen to form carbon dioxide, water, heat and light

Note:Balanced reaction conserves the number of each atom species.

To cite this page:
Lecture IV: Atoms and Molecules
[Saturday, 20-Oct-2018 22:03:01 EDT]
Edited by: on Sunday, 03-Oct-2010 16:32:50 EDT