•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.