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Structure of the Atom Electrons Protons Neutrons Protons and neutrons make up the nucleus (the majority of the mass of the atom) Electrons are located outside of the nucleus. Electrons are located in orbitals…an orbital is a 3dimensional region of space where the probability of finding the eletron is high. Properties of Fundamental Particles Particle Charge Mass Electron -1.6022 x Proton 10-19 coulombs 9.109 x 10-28 g +1.6022 x 10-19 coulombs 1.673 x 10-24 g 1.675 x 10-24 g Neutron 0 Today’s DCI DCI #3 distributed on today. 1 Atomic Number The number located above the element’s symbol. The atomic number is equal to the number of protons for the element. The symbol used to represent atomic number is Z. The atomic number is just a number. Atomic Mass The number located below the element’s symbol. No units listed in the periodic table…we must remember the units of the atomic mass are atomic mass units. The symbol for atomic mass units is u. For hydrogen the atomic mass is 1.00797 u. The mass of a hydrogen atom is 1.6736 x 10-24 g. Atomic Mass Too convert from atomic mass units to grams we need a conversion. By definition the relationship between atomic mass units and mass in grams is defined as 1/12 of the mass, in grams, of the isotope of carbon that contains 6 protons, 6 neutrons and 6 electrons. 1 u = 1/12 * 1.99268 x 10-23 g = 1.66057 x 10-24 g 2 Atomic Mass The mass in grams of a hydrogen atom is, 1.6736 x 10-24 g * (1 u/1.66057 x 10-24 g) = 1.0078 u Hmmm…what is up?…if the atomic mass for the element hydrogen is 1.00797 u how did we arrive at a mass of 1.0078 u for hydrogen? We much consider that there are three different isotopes of hydrogen that contribute to the atomic mass of hydrogen listed in the periodic table. Relative Weighted Average Atomic Mass Look at Weighted Average in your During Class Inventions and Computer Lab Activities workbook. Relative Weighted Average Atomic Mass For hydrogen: Symbol Atomic Mass (u) % Abundance 20Ne 21Ne 19.99244 20.993846 90.48 0.27 22Ne 21.991385 9.25 3 Relative Weighted Average Atomic Mass For hydrogen: Symbol Atomic Mass (u) % Abundance 20Ne 21Ne 19.99244 20.993846 90.48 0.27 22Ne 21.991385 9.25 RWAAM = Σ(Relative Weight*fractional abundance)I Relative Weighted Average Atomic Mass For hydrogen: Symbol Atomic Mass (u) % Abundance 20Ne 21Ne 19.99244 20.993846 90.48 0.27 22Ne 21.991385 9.25 RWAAM = Σ(Relative Weight*fractional abundance)I RWAAM = (19.99244 u *0.9048 + 20.993846 u *0.0027 + 21.991385 u*0.0925) RWAAM = 18.08916 u + 0.0566834 u + 2.03420 u RWAAM = 20.1800434 u Chapter 1 4 Chapter 2 Metals Nonmetals Metalloids Ions cations: Na+, Ca2+, Al3+, Fe3+ anions: Cl–, O2– , N3– Compounds ionic: formula contains metal and a nonmetal element covalent: formula contains nonmetal elements 5