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Discovery of the Nucleus

Discovery of the Nucleus - fire massive alpha particles at...

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Discovery of the Nucleus Radioactivity o heavy elements are radioactive o electric field resolves radiation into 3 components: alpha, beta, and gamma Table: hypothetical description of alpha particles based on properties of alpha radiation observation hypothesis alpha rays don't diffract ... alpha radiation is a stream of particles alpha rays deflect towards a negatively charged plate and away from a positively charged plate ... alpha particles have a positive charge alpha rays are deflected only slightly by an electric field; a cathode ray passing through the same field is deflected strongly ... alpha particles either have much lower charge or much greater mass than electrons Ernest Rutherford's scattering experiment o hypothesis: If the plum pudding model of the atom is correct, atoms have no concentration of mass or charge (atoms are 'soft' targets) o experiment to test hypothesis:
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Unformatted text preview: fire massive alpha particles at the atoms in thin metal foil alpha particles should pass like bullets straight through soft plum pudding atoms o observation: a few alpha particles ricocheted! o new hypotheses: all of the positive charge and nearly all of the mass of the atom is concentrated in a tiny, incredibly dense 'nucleus', about 10-14 m in diameter electrons roam empty space about 10-10 m across, around the nucleus • Composition of the Nucleus o nuclei are composed of "nucleons": protons and neutrons o atomic mass units 1 amu (aka 1 dalton) = exactly 1/12 the mass of a carbon-12 nucleus 1 dalton = 1.67 x 10-24 g Table: Subatomic particles important in chemistry. particle symbol charge mass, kg mass, daltons electron e--1 9.10953× 10-31 0.000548 proton p+ +1 1.67265× 10-27 1.007276 neutron n 1.67495× 10-27 1.008665...
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Discovery of the Nucleus - fire massive alpha particles at...

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