Download The Atom Nucleus Subatomic Particles Atomic Number Isotopes

Nucleus Contains 99.9% of the mass of the atom n 100 times smaller than the atom n The “core” of the atom n The Atom Chapter 3 Subatomic Particles n Atomic Number Proton (p + )—positive charge n n Neutron (n 0 )—no charge n Electron (e ­ )—negative charge n n The number of protons in an element Determines the element n The atomic number for that particular element will never change. n Found in nucleus n Found in nucleus n Found in shells outside the nucleus Isotopes Atoms can have different number of neutrons! n Atoms of the same element that have the same number of protons, but different number of neutrons are isotopes. n EX: oxygen will always have 8 protons helium will always have 2 protons Mass number n Mass # = atomic # + number of n 0 The mass # of Carbon is: n The mass # of Carbon is: n Notation: Write the name of the element and the mass # for the isotope. n The atomic mass is the average of all of the element’s isotopes. n 6 protons + 6 neutrons = 12 6 protons + 8 neutrons = 14 n n EX: Carbon­12 and Carbon­14 EX: The atomic mass for Carbon is 12.011
1 Atomic Models n Niels Bohr n Electrons move in definite “orbits” around the nucleus (like planets) n Energy levels are located at certain distances from the nucleus Electrons Electron Cloud—the entire space that the electrons occupy. n Energy levels represent the most likely location in the cloud in which an electron can be found. n Higher levels are farther from the nucleus n Bohr Atoms n n n n n n Each level can only hold a certain number of electrons 1 st : 2 electrons 2 nd : 8 electrons 3 rd : 18 electrons Quarks—make up all particles in the nucleus Thought that all particles are made up of 3 quarks. http://www.colorado.edu/physics/2000/quantumzone/bohr.html Wave Model n Wave Model n n Electrons do not move in definite paths Impossible to locate the exact location of electron n n EX: Finding your friend at a concert Atom has a small positively charged nucleus surrounded by a region of electrons
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