CHEM 1101- Midterm Exam Guide - Comprehensive Notes for the exam ( 42 pages long!)
11 Oct 2017
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Chapter 2 atoms and the periodic table. Greek philosophers questioned the fundamental nature of matter. Aristotle: matter could be divided infinitely = wrong. Democritus: there is a limit = correct (smallest an element can be divided and still identifiable as the element is an atom ) Only whole atoms can combine: chemical reactions change only the way atoms are combined in compounds. Atoms are composed of tiny subatomic particles (protons, neutrons & electrons) Neutrons have a mass similar to that of a proton, but electrically neural. Electrons have a small mass (only 1/1836 that of a proton) & carry a negative electrical charge. So much lighter than protons and neutrons that their mass is usually ignored. Masses of atoms and subatomic particles = expressed on a relative mass scale. Basis for scale is an atom of carbon that contains 6 protons & 6 neutrons. It"s just because 1. 672622 x 10 -24 g (mass of a proton) is very inconvenient.
