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Topic 4: Atomic Structure ALL atoms are made up of combinations of three basic ‘subatomic’ particles... Protons Electrons Neutrons PROTON Charge: Positive (+) Location: Nucleus Size: Large (same as neutron) Mass: 1 amu ELECTRON Charge: Negative (-) Location: Orbiting the Nucleus Size: Small (about 1/2000th the size of protons or neutrons) Mass: 0 amu (too small to count) NEUTRON Charge: Neutral (o) Location: Nucleus Size: Large (same as proton) Mass: 1 amu Ode To A Proton by Shay Heather Davies - 19th May 1998 Oh proton, how your positive charge makes me blush! I watch you from a distance, and my heart turns to mush... If only I was a neutron, we could frolic for awhile, and then my dear I'm sure, I would wear a permanent smile. But alas, I'm an electron, and I must watch you from afar, so far from where you are... It seems to me that my fate is sealed, but how can my love not be revealed? My mass won’t be complete until you’re mine, so give me this chance, and show me a sign. Some day we’ll meet and I'll see your eyes, and we will be together and neutralize... so until that day, farewell my opposite attract, my love for you remains intact. Important numbers for each type of atom… each ‘element’: Atomic mass - Atomic Number = # of neutrons (total mass of protons and neutrons) (total number of protons) Some atomic masses may be written as a decimal (e.g. Carbon is actually 12.01, not ‘12’) This is because some elements have atoms with varying numbers of neutrons in the nucleus. We call these different atoms of the same element ‘ISOTOPES’ Example #1 : Isotopes of Hydrogen Atoms of elements always have equal numbers of protons (positive charges) and electrons (negative charges). The number of neutrons (which are neutral) an atom has can vary. NOTE: Tritium NOT Titrium Example #2 : Isotopes of Carbon Carbon-14 doesn’t have a special name as the isotopes of hydrogen do. It is the isotope of carbon we use to ‘date’ how old something is. Note that the ‘% Today’ (usually written as ‘% abundance’) is an indication of the fraction of ALL carbon that is of that particular isotope.