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Unformatted text preview: a particular type of radioactive rays (Alpha rays) through thin metallic foils
· Alpha (a) rays consist of a stream of particles (a particles) which: Ø are positively charged Ø are relatively heavy (four times as heavy as the H atom) OBSERVATIONS INTERPRETATIOINS
· Most of the aparticles pass through · The gold atom is mostly occupied by lightweight electrons that the gold foil.
cannot deflect the apartilces.
· A very small part of the atom is dense (contains most of its mass) · A few aparticles (1 in 8000) were and is positively charged.
scattered at large angles and sometimes deflected back. 6 Chemistry 101 Chapter 2 ATOMIC MODEL Conclusion:
· The nuclear model of the atom contains a nucleus and electrons surrounding them. · · · · · · VI. NUCLEUS Located at the center of the atom
Contains all the protons
Is positively charged
Contains most of the mass of the atom
Is very small
Is very dense ELECTRONS
· Are located outside the nucleus
· Are negatively charged
· Have negligible mass
· Occupy most of the volume of the atom The Discovery of the Neutron
· James Chadwick discovered in 1932 that the atom contains a third subatomic particle called neutron.
· The neutron: Ø is located in the nucleus Ø is electrically neutral Ø has about the same mass as the proton Properties of Subatomic Particles Particle Relative Mass Electr...
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