•Very
small (for 1H: mass = 1.67´10-27 kg Diameter = 0.4
nm = 4´10-10 m)
•
•Composed
of an even smaller nucleus and an “orbiting” cloud of
electrons
–Nucleus is very small even compared to size of atom
(for 1H: D=1.6 ´10-15 m)
•So atoms are mostly empty space
–Nucleus contains almost all the mass and is
positively charged
–Electrons are negatively charged and usually balance
charge of nucleus
–
•Almost
like a miniature solar system: Sun
Þ Nucleus, Planets Þ Electrons
–Like solar system, atoms are mostly empty space (nucleus small)
–Like solar system, force is 1/r2, but from electric attraction, not gravity
–Unlike solar system, need to use Quantum Mechanics,
not Newtonian Mechanics
•Only certain Electron “Orbits” will be
allowed by Q.M.