Topics of Discussion Summarize the Development of Atomic Theory Examine Atomic Structure
Laws Law of Conservation of Mass Law of Definite Proportions Law of Multiple Proportions
Laws Law of Conservation of Mass Mass is neither Destroyed nor Created during ordinary Chemical or Physical Reactions
Laws Law of Definite Proportions A Chemical compound contains the same elements in exactly the same proportions, by Mass, regardless of size of sample or source of compound
Laws Law of Multiple Proportions If 2 or more different compounds are composed of the Same 2 Elements, then the ratio of the 2 nd. element combined with the a certain mass of the 1 st. element is always a ratio of small whole numbers
Development of Atomic Theory Democritus –Believed that matter was made up of atoms –Atoms were invisible particles –Atoms were indestructible particles –Lost out to Aristotle who stated that matter was continuous
Development of Atomic Theory Dalton (1808) Explains the Laws of conservation of mass, definite proportion and multiple proportion –Elements are composed of extremely small particles called atoms –Atoms of the same element are identical in size mass and properties. Atoms of different elements differ in size. Mass and properties
Development of Atomic Theory Dalton (1808) cont. –Atoms cannot be subdivided, created, or destroyed. –Atoms of different elements combine in simple whole-number ratos to form chemical compounds –In chemical reactions, atoms are combined, separated or rearranged
Development of Atomic Theory J.J. Thomson (1897) Discovers the electron –(mass and a high charge) Proposes the Plum-Pudding model –Atom is neutral –Electrons embedded in a sphere of positive charge
Development of Atomic Theory Rutherford (1911) Gold foil experiment Discovers that the atom has a nucleus –Extremely small –Extremely dense –Positive charge Electrons move around the nucleus
Development of Atomic Theory Bohr (1913) Electrons circle nucleus in specific circular paths at fixed distances from the nucleus Each electron orbit has a Specific Energy or energy level A Quantum of energy is required to move from one orbit to the next Works for Hydrogen only!
Development of Atomic Theory Millikan discovers electron charge and Mass of an electron (1909) Chadwick discovers Neutron (1932) De Broglie proposes particle wave behavior of Electron (1923) Schrödinger writes an equation to determine probability of electron location
Development of Atomic Theory Electron Cloud Model (present) Based on Schrödinger's wave equation Visual model of the probable locations of the electron in an atom
Atomic Structure Properties of sub-atomic particles (proton, neutron, & electron) –C–Charge –L–Location in Atom Symbols A(mass number) & Z (atomic number)
PROTON –Location –Charge –Symbol Center of atom; nucleus area Positive p ATOMIC NUMBER (Z) = number of protons in the atom
Atomic Structure Neutron –Location –Charge –Symbol Center of atom; nucleus area No charge (0) n To find the number of neutrons in an atom : Mass number of the element – number of protons (atomic number) = A (number of neutrons
Atomic Structure Electron –Location –Charge –Symbol In shells around the nucleus of the atom. Negative e In a neutral atom, # of electrons = # of protons
Atomic Structure IONS Ions are charged particles. Atoms gain or lose ELECTRONS are ions. Lose e - --- more positive --- positive charge Gain e - --- more negative ---negative charge Na lose 1e - = Na 1+ (11 + + 10 - = 1 + )
Atomic Structure ION# p + #e - Cl 1- Mg 2+ Fe 3+ 17 18 12 10 2623
Atomic Structure Isotopes are: –Atoms of the same element –That have different masses Naturally occur or man made
Atomic Structure Practice: 1. Element D has 6 protons and 7 neutrons. Element F has 7 protons and 7 neutrons. 2. Element J has 27 protons and 32 neutrons. Element L has 27 protons and 33 neutrons. 3. Element X has 17 protons and 18 neutrons. Element Y has 18 protons and 17 neutrons. 4. Element Q has 56 protons and 81 neutrons. Element R has 56 protons and 82 neutrons.
Atomic Mass Average Atomic Mass –Weighted average –Of all naturally occurring isotopes This is the mass on the Periodic Table This is the mass we use for calculations Can you calculate a weighted average?
Atomic Mass ISOTOPE % in NatureMASS Copper-6369.17%62.929599 amu Copper-6530.83%65.927793 amu 100.00%
Atomic Mass ISOTOPE % in NatureMASS Carbon-12 98.89%12.000 amu Carbon-13 1.11% 13.003 amu 100.00%