Chem Notes 090110 - bubble but failed Next tried nucleus...

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Chapter 2: Law of conservation of mass: within a controlled environment, despite chemical changes, the mass of all matter remains the same. Law of Definite Proportions: That all pure compounds have a consistent proportion of atoms/weight. --at the time, were unaware of amount of atoms, etc. did it by weight—found that the ratio of hydrogen to oxygen in terms of gram was always the same. Cathode Ray Tubes: a tube with a positive end and a negative end, and found that the atoms gravitated towards the positive side, implying that there was something that was negatively charged (opposites attract). --found that electrons were 2000 times lighter than a hydrogen atom, which at the time they thought was the smallest thing Make-up of atom was a question, since for sure positive charged as well to balance out. --first tried jelly-type model where the electrons were contained within a positive charged
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Unformatted text preview: bubble, but failed Next tried nucleus model, with electrons and protons around it. However, not heavy enough to account for full weight, so discovered the neutron, which sat in the nucleus and was very dense. Mass of electron: 0.00091*10-27 kg--created the atomic mass unit (the amu ) amu of protons and neutrons is 1, and electron is 0. Elements are deFned by their protons, or their A²OMIC NUMBER, or by their CHEMICAL SYMBOL Atoms with the same number of protons but di³erent numbers of neutrons is an ISO²OPE An elements mass number is its protons plus neutrons--therefore an element is wri±en with its atomic number on the bo±om and the mass number on the top If you change the number of electrons, becomes an ION. PosiTvely charged ions are caTons, while negaTvely charged ions are anions....
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