ATOMIC THEORY Honors Chemistry

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

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 Element-A# p + #n 0 #e - Beryllium-9 Oxygen-16 Sulfur

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+ ( = 1 + )

Atomic Structure ION# p + #e - Cl 1- Mg 2+ Fe

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 % amu Copper % amu %

Atomic Mass ISOTOPE % in NatureMASS Carbon % amu Carbon % amu %