SUMMARY OF MODELS OF THE ATOMMODEL MAIN POSTULATES WHAT MODEL EXPLAINS GREEK MODEL An atom is a hard spherical indivisible particle. Physical properties of matter DALTON MODEL Atoms cannot be created or destroyed. Chemical change is the union or separation of atoms. Laws of chemical change THOMSON RAISIN BUN MODEL An atom is a sphere of uniformly distributed positive charge with electrons embedded throughout. Location of protons and electrons. RUTHERFORD NUCLEAR MODEL An atom is mostly empty space with all of the positive charge and most of the mass located in a central part called a nucleus. Scattering of alpha particles by metal foils.BOHR MODEL The energy of an electron is quantized. Electrons travel around the nucleus in circular paths called orbits. Atomic line spectrum of hydrogen. QUANTUM MODEL An electron has the properties of both a particle and a wave. Since its location cannot be determined exactly, we can speak only of the region in which it is most likely to be found (an orbital). Line spectra of many-electron atoms and quantization of the energy of the electron.
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THE STRUCTURE OF THE ATOMNucleonsare protons or neutrons. The Atomic Numberis the number of protons in the nucleus and is designated by the letter Z. The Mass Numberis the total number of protons plus neutrons in an atom and is designated by the letter A. Also the Mass Number is approximately equal to the mass of the atom (in atomic mass units). ATOMIC STRUCTURE SYMBOLSIn general, atoms are symbolized as follows: mass number AXatomic symbol Zatomic number Isotopesare atoms having the same number of protons but different number of neutrons. That is, the atoms have the same atomic numbers but different mass numbers.