Based on second postulate: atoms are neither created or destroyed (under normal chemical reactions).
Based on third postulate, atom ratio is fixed, so mass must be constant.
Applies where two elements, A and B, form more than one compound.
Name | Mass(amu) | Charge | Location |
proton (p+) | 1 | +1 | nucleus |
neutron (n0) | 1 | 0 | nucleus |
electron (e-) | 0.0005 | -1 | outside the nucleus |
m/e = 5.69x10-9 g/coulomb
found the mass to charge ratio.
Combine Thomsons and Millikans work and obtain the mass of a single electron
m = (1.60x10-19 coulomb)(5.69x10-9 g/coulomb) = 9.11x10-28 g
[1 p+ is 1.67x10-24 g, therefor (1.67x10-24g)/(9.11x10-28 g) = 1833 about 200 times larger or 1/2000 or .005]
carried out by Johannes Geiger and Ernest Marsden.
Mass number = #(p+ + n0) = number of protons plus number of neutrons
Atoms of the same element can differ in mass number, isotopes.
protuim (light hydrogen), deuterium, tritium
U235 and U238
Symbol 23592U and 23892U
To calculate atomic mass you must know two things: the masses of the individual isotopes and the percentages that these isotopes exist in nature.
Ne-20 | 20.00 | 90.92% |
Ne-21 | 21.00 | 0.26% |
Ne-22 | 22.00 | 8.82% |
This page was made by Erik Epp.