DVD: USING THE PERIODIC TABLE

(NOTES)

January 7, 2014

  • Over 100 elements have been discovered
  • Each element has a unique set of properties and behaviors.
  • Periodic table used to identify the similarities and differences of elements
  • If you know the location of an element on the periodic table you can determine their properties and how they will react.
  • Dmitri Mendeleev: 1869 organized first periodic table
  • Group/family are vertical
  • Undiscovered elements have empty spaces
  • Rows called periods
  • The first period Hydrogen (H) and Helium (He)
  • Light, colorless, odorless, tasteless at room temperature
  • Make up most of the universe (9 out of 10 elements in universe are H, the rest are He)
  • H makes the sun and stars shine
  • nuclear reaction, releases tremendous energy and produces He
  • Key Point: Nuclear reactions
  • Key Point: Chemical reactions involve electrons
  • Dot structures (valence electrons)
  • Hydrogen (H) has one electron (one dot)
  • Helium (He) has two electrons (two dots)
  • Period one elements have one energy level and can hold a maximum of two electrons.
  • When an energy level is full, it is stable
  • When an energy level is not full, it is unstable
  • He does not react with other elements and stable
  • H forms many bonds
  • Second Period
  • Gradual transition from shiny, solid metals to gaseous non-metals
  • Key Point: metals get harder and less reactive from left to right and nonmetals get more reactive from left to right
  • Lithium, lightest and softest, reacts with air and water
  • Beryllium less reactive, most toxic elements
  • Key Point: metalloid is an element with a blend of metallic and non-metallic properties.
  • Boron (B) less reactive than Be
  • carbon atoms bond to one another indefinitely
  • example, diamond
  • Nitrogen (N) (diatomic, gas, non-metal)
  • Oxygen (O) (diatomic, gas non-metal) reactive and highly flammable
  • Fluorine (F), (gas, non-metal) highly reactive, can form explosive compounds
  • Neon (Ne), (unreactive gas, on-metal)
  • electron arrangement determines reactivity
  • have second energy level
  • Key Point: only electrons in the valence shell (level) are involved in chemical reaction.
  • valence electrons are shown as dots around the symbol
  • valence electrons determine the reactivity of an element
  • Key Point: Every period ends with a noble gas
  • most reactive elements Li and F
  • noble gases are non-reactive
  • most reactive elements are closest to noble gases on the table
  • Trends of metal reactivity
  • 75% of elements are metals
  • The easier it is for an element to loose electrons, the more reactive it is
  • smaller atoms, easier to loose electrons
  • group one electrons loose one electron
  • Key Point: Ionization energy is the energy required to pull electrons away from an isolated atom.
  • groups two looses two electrons
  • Alkali Metals (group/family 0ne)
  • Never found uncombined in nature
  • Need to be stored in oil or gas to avoid reactivity
  • The lower the element on the table, the more violent the reaction (more reactive)
  • Alkali Earth Metals (group/family two)
  • React slower than group one
  • used in fireworks
  • metals share valence electrons (sea of electrons)
  • harder than group one
  • Key Point: semiconductors only conduct electricity at high temperatures
  • Group 13 (aluminum Group)
  • All group 13 react and release lots of energy
  • low melting points
  • Group 3-12 Transition metals
  • Elements differ in properties
  • There is not pattern because of partially filled levels
  • don’t have a pattern in valence electrons
  • Group 14 Carbon Family
  • C does not conduct electricity in diamond form, covalent bonds (nonmetal)
  • atoms react like a metal if the electrons are easier to pull
  • as the elements go down in the group, the more metallic its behavior (same for groups 13-16)
  • Location of elements is based on its behavior and properties
  • Group 13-16
  • Elements become more metallic as they go down on the table.