The Atom

Atom The smallest unit of matter

Democritus 5th Century B.C.E. Keep breaking material farther down Eventually you would have an ‘atom’- unable to be cut

Dalton 1803 Billiard Ball Model An atom is a solid sphere All elements are made up of the same atom

Thomson 1897 Plumb Pudding Model The sphere of the ‘billiard ball’ is positive with negative charges spread throughout

Rutherford 1908 The ‘billiard ball’ is positive in the middle There are negative spheres surrounding the positive middle

Neils Bohr 1915 Electrons travel in orbits around the positive middle Orbits are a specific shape

Nucleus Consists of Protons and Neutrons Protons- positive charge Neutrons- neutral/no charge Electrons Negative charge 2 electrons in 1st ring 8 electrons in 2nd ring Valence electrons: electrons in outer ring

Neutral Atom Same number of electrons as there are protons

How to Draw an Atomic Diagram of an Element Determine number of protons & electrons in element Look at atomic # Draw nucleus as a circle- write # of protons in the circle Add 1st electron orbital with appropriate # of electrons stop at 2 e- Add 2nd orbital with appropriate # of electrons stop at 8 e- Completed when all electrons add up to atomic # Electron Orbital Maximum # electrons 1st 2 2nd 8 3rd 18 4th 32

Draw the atomic diagram for Phosphorus

Ion Atom with a positive or negative charge Negative- extra e- Positive- missing e-

Aston Discovered the Isotope Isotope Same number of protons and electrons Different number of neutrons Changes the overall weight of the atom

Elements Element: Consists entirely of ONE type of atom Roughly 100 elements Metals Non-metals Gases Shiny Little to no shine -------------------------- High Boiling Temperature Varies Solid at room temperature (except mercury) Solid (brittle) or liquid at room temperature Gas at room temperature Good conductors of heat and electricity Poor conductors of heat and electricity ---------------------------- Left side/middle of the periodic table Upper right side of periodic table Right-most column on periodic table

Name of Element Symbol Carbon Oxygen Hydrogen Nitrogen Chlorine Phosphorus Silicon Fluorine Magnesium Sodium

Periodic Table Rows: 1. Not alike in properties First element a solid, last element is a gas Atomic mass increases from left to right Columns: Alike in properties Same number of valence electrons