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Atomic Structure The atom as we understand it today Atomic Structure The atom consists of 3 subatomic particles? Do you know what they are? Proton Electron Neutron Atomic Structure The following notation is used: A X Z A = Mass Number Z = Atomic Number Atomic Structure Atomic Number (Z) – this is unique to each atom. The atomic number is equal to the number of protons. Mass Number (A) – this is the total mass of each atom. Remember, each P and N has a mass of about 1amu. amu = 1/12 the mass of a C-12 atom Therefore, the mass number = #P + #N Atomic Structure The atom written as 3617Cl can also be expressed as Cl-36. The 17 is understood, because we are referring to the chlorine atom. The 36 refers to the Mass Number. Atomic Structure Element C-12 F-14 N-14 Na-25 Li-8 Atomic # Make the following grid in your notes: Mass # #P #N #e Atomic Structure Element Protons 119 Make the following grid in your notes: 238 50Sn 92U 17 85 Neutrons 92 Electrons 82 Atomic Number Mass Number 36 92 92 235 Atomic Structure Can we have both U-235 and U-238? Yes! They are referred to as Isotopes. Isotopes are atoms of the same element (they have the same number of P) but they contain a different number of Neutrons. (This is what changes the mass number) Atomic Structure Now what do we do when we are given: 60 Co2+ 27 We now have: P: 27 N:33 e-: 25 (We have two fewer electrons than P) Atomic Structure ***WARNING*** Never change the number of protons when a charge is present, ALWAYS change the number of e-. A positive charge (More P than e-) A negative charge (More e- than P) Atomic Structure Element Protons 25 Make the following grid in your notes: 2+ 126 12Mg 85 18 26 28 Atomic Number Mass Number 3+ 17 Neutrons Electrons 51Sb 36 10 51 13 27