7 Dalton’s Atomic Theory All matter is made of tiny indivisible particles called atoms.Atoms of the same element are identical, those of different atoms are different.Atoms of different elements combine in whole number ratios to form compounds.Chemical reactions involve the rearrangement of atoms. No new atoms are created or destroyed.
8 Just how Small is an Atom? Think of cutting a piece of lead into smaller and smaller piecesHow far can it be cut?An atom is the smallest particle of an element that retains the properties of that element
9 J. J. Thomson - English physicist. 1897 Parts of AtomsJ. J. Thomson - English physicist. 1897Made a piece of equipment called a cathode ray tube.It is a vacuum tube - all the air has been pumped out.
38 + Atom is mostly empty. Small dense, positive piece at center. How he explained itAtom is mostly empty.Small dense, positive piece at center.Alpha particles are deflected by it if they get close enough.+
44 Matter and AtomsNucleuse-p+ProtonsElectronsnNeutrons
45 Elements Chemical Symbols Structure of the Atom one type of atom. Substances made up of onlyone type of atom.Chemical SymbolsA shorthand way to write thenames of the elements.
46 # of protons = # of electrons Atomic NumberThe number of protonsin an atom.In a neutral atom# of protons = # of electrons
47 Atomic mass - # of protons The number ofprotons and neutronsin an atom.# of neutrons =Atomic mass - # of protons
48 The average of the atomic mass of all the isotopes of that element. Average Atomic MassThe average of the atomic massof all the isotopes of that element.
49 Atoms of the same element with different number of neutrons. IsotopesAtoms of the same element with different number of neutrons.1P+0N1e-Protium1P+2N1e-Tritium1P+1N1e-DeuteriumAverage Atomic Mass for H =
50 Atomic Number (# of Protons) 15PhosphorusPSymbolAverage Atomic Mass(31)Name
51 ) ) ) 2e- 8e- 5e- Element: Phosphorus # of Protons: 15 15p+ # of Neutrons:31 –15 = 1616nº# of Electrons:15)2e-)8e-)5e-
65 Electron Configuration Where the electrons are in the orbitals of the atom.The most stable configuration is the one in which the electrons are in orbitals with the lowest energy.Lowest Energy of the electrons is called the Ground State.
66 ) ) ) 2e- 8e- 5e- Element: Phosphorus # of Protons: 15 15p+ # of Neutrons:31 –15 = 1616nº# of Electrons:15)2e-)8e-)5e-