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I. Subatomic Particles (p.113 - 114) Particle Symbol Location Charge Relative Mass (amu) electron e- Electron cloud – proton p+ nucleus + 1 neutron n0 nucleus 0 1 1/1840 approx 0 Actual Mass (g) 9.11 x 10-28 1.67 x 10-24 1.67 x 10-24 Elements are listed by their chemical symbols Symbols are usually either one capital letter like C for Carbon, or one capital and one lowercase letter like Ne for Neon The periodic table gives much information we need to learn more about the atom of each element Atomic number = # of protons in an atom Whole number shown on periodic table Periodic table is arranged by atomic number The average atomic mass is the number at the bottom of this square Found by averaging the natural abundances of its isotopes Weighted average Atomic Number Symbol Element Name Atomic Mass Protons Protons Electrons Neutrons # n0 = Atomic mass – Atomic number ATOM ATOM NUCLEUS NUCLEUS ELECTRONS ELECTRONS PROTONS PROTONS NEUTRONS NEUTRONS POSITIVE CHARGE NEUTRAL CHARGE NEGATIVE CHARGE NEGATIVE CHARGE equal in a = Atomic mass Most of the atom’s mass. Atomic Number neutral - Atomic # atom equals the # of... QUARKS #n0 Quarks ◦ component of protons & neutrons ◦ 6 types 3 quarks = 1 proton or 1 neutron He II. How Atoms Differ (p. 114 - 121) Mass Number Isotopes Relative Atomic Mass Average Atomic Mass mass # = protons + neutrons always a whole number NOT on the Periodic Table! © Addison-Wesley Publishing Company, Inc. Atoms of the same element with different numbers of neutrons Isotope notation: Mass # Atomic # Element name Mass # Isotope name: carbon-12 12 6 C © Addison-Wesley Publishing Company, Inc. Chlorine-37 ◦ atomic #: ◦ mass #: Isotope notation: 17 ◦ # of protons: 37 ◦ # of electrons: 17 ◦ # of neutrons: 17 20 37 17 Cl Most elements are found as mixtures of isotopes Relative abundance of each isotope is the same in each source 12C atom = 1.992 × 10-23 g atomic mass unit (amu) 1 amu = 1/12 the mass of a 12C atom 1 p = 1.007276 amu 1 n = 1.008665 amu 1 e- = 0.0005486 amu © Addison-Wesley Publishing Company, Inc. weighted average of all isotopes on the Periodic Table round to 2 decimal places Avg. Atomic Mass (mass)(% ) (mass )(% ) 100 EX: Calculate the avg. atomic mass of oxygen if its abundance in nature is 99.76% 16O, 0.04% 17O, and 0.20% 18O. Avg. (16)(99.76 ) (17)(0.04) (18)(0.20) 16.00 Atomic 100 amu Mass EX: Find chlorine’s average atomic mass if approximately 8 of every 10 atoms are chlorine-35 and 2 are chlorine-37. Avg. Atomic Mass (35)(80) (37)(20) 35.40 amu 100