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Chapter 18 Notes- Structure of the Atom Review: Element matter composed of one type of atom. Chemical symbols are the one or two letter abbreviations for elements, either one capital letter or two letters, first capital, second lower case. Atomic Components: Atom: smallest piece of matter that retains the element’s properties, composed of particles called protons, neutrons and electrons Nucleus: center of atom, positively charged, containing protons and neutrons, contains most of the mass of an atom Proton: particles with a charge of +1, (mass of 1 amu), Neutron: neutrally charged particles (mass of 1 amu) Electron cloud: area around the nucleus where electrons are most likely to be found Electrons: particles with a charge of -1 (mass of 1/1,836 amu) How to identify elements: -Atomic number is the number of protons in an atom, it identifies the element -Neutral atom has same number of protons and electrons 18.2 Isotopes Average atomic mass – the average of the mass numbers of all the same kind of atoms Mass number – the most stable isotope, the amount of protons and neutrons in an atom (round the atomic mass) PROTONS + NEUTRONS = MASS NUMBER MASS NUMBER - PROTONS = NEUTRONS Isotope- atoms of the same element with different numbers of neutrons Carbon-14 Carbon-12 6p 6e 8n 6p 6e 6n
