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  • 1. Unit 3, Part 1 The Periodic Table Chemistry Notes
  • 2. What is Periodicity?
    • Means to occur at regular periods/intervals
    • In chemistry, it applies to the Periodic Table – the arrangement of elements and their chemical properties
  • 3. The Periodic Law
    • Chemical and physical properties of elements are functions of their ATOMIC NUMBERS
    • Periodic means to repeat
    • 1st proposed by Dmitri Mendeleev, who related periodic functions to atomic mass
  • 4. The Periodic Table
    • Graphical representation of the Periodic Law
    • Elements positioned according to atomic number and electron structure
    • Long and short forms
  • 5. Organization of P.Table
    • Group = vertical column
    • Period = horizontal row
      • Elements in the same row have the same number of occupied energy levels .
      • So…
      • Period = Energy Level in Atom
      • There are 7 periods…
  • 6. The Zig-Zag Line
    • The “Stair case” on the P.Table
    • Metals – to left
    • Nonmetals – to right
    • Metalloids (semi-metals) – along stair case
    http://img.sparknotes.com/content/testprep/bookimgs/sat2/chemistry/0001/sat117002_0407.gif
  • 7. Properties of Metals
    • Luster (shiny)
    • Conduct heat, electricity
    • Malleable (sheets)
    • Ductile (wires)
    • Solid, except for Mercury (liquid )
    • Low numbers of outer (valence) shell electrons
    • High density
    • Most have high melting points
    Nonmetals – have opposite characteristics!
  • 8. Metalloids
    • Often called semi-metals
    • Properties of both metals & nonmetals
    • Often used as semi-conductors (Si, Ge)
    Alloys
    • Mixture of metals
    • Changes properties – usually for the better
    • Example = brass (Zn, Cu); sterling silver (Ag, Cu)
  • 9. The Representative Elements
    • A elements (main-group)
    • Groups 1A – 8A
    • Have a wide range of properties
    • Elements in the same group (A elements) have the same number of valence electrons, which corresponds to the group number (ex: 6A = 6 valence e-)
      • Valence Electrons – in outermost energy level; most likely involved in a chemical reaction
  • 10. Types of Representative Elements
    • 1A = Alkali Metals
    • --soft
    • --very reactive – esp. in water
    • --found in nature in compound form
    • --tend to lose 1 electron (form +1 ions)
    • 2A = Alkaline Earth Metals
    • --quite reactive, also found in comp’d form
    • --tend to lose 2 electrons (form +2 ions)
    • (takes more energy to lose 2 electrons!)
  • 11.
    • 6A = Chalcogens
    • --tend to gain 2 electrons (form -2 ions)
    • --nonmetals
    • --oxygen & sulfur – exist in “pure form”
    • --others – are ions within metal ores
    • 7A = Halogens
    • --most reactive of nonmetals
    • --react w/metals to form salts (halides)
    • --gain 1 electron (form -1 ions)
    Types of Representative Elements
  • 12.
    • 8A = Noble Gases
    • --mostly unreactive (inert)
    • --outer energy level is filled, so overall charge is zero
    • --helium also has a filled outer level, so it is placed in the noble gas column
    • Hydrogen
    • --most common in universe; very reactive
    • --has 1 p + and 1 e -
    • --will lose 1 e - and form +1 ion
    Types of Representative Elements
  • 13. Transition Elements
    • B elements (metals)
    • Arrangement of electrons in outer energy levels vary, so common ion charge changes
    • Lose different numbers of valence electrons depending on the reaction
    • Degree of reactivity…and therefore properties…varies by element
    • Common Ion Charge = +2
  • 14. Lanthanides & Actinides
    • Bottom of P.Table
    • Lanthanides (follow Lanthanum)
      • Properties of Metals
      • Similar to 2A elements
    • Actinides (follow Actinium)
      • radioactive
  • 15. Trend #1 – Ionization Energy
    • Energy needed to remove an electron from an atom
    • General Trend = increases to the right and up
      • Electron Shielding – outermost e- are held less tightly to nucleus, so easier to lose them (in elements to left)
    http://www.shodor.org/chemviz/ionization/students/background.html
  • 16. Trend #2 - Electronegativity
    • How strongly an atom attracts electrons (to itself) in a bond, particularly when e- are shared, which is called covalent bonding.
    • General Trend = increases to the right and up
    http://grandinetti.org/Teaching/Chem121/Lectures/Electronegativity/assets/ElectronegativityTrends.gif
  • 17. Trend #3 – Atomic Radius
    • Essentially – size of atom
    • Determined by calculating bond radius
    • Size depends on volume occupied by electrons, which can change with state of matter and movement of e-
    • General Trend = increases to left and down
    http://www.shodor.org/chemviz/ionization/students/background.html
  • 18. Trend #4 – Ionic Radii
    • Cations (+ charge)
      • Generally smaller than parent atom because of electron loss
      • Example: Ca | Ca 2+
    • Anions (- charge)
      • Generally bigger than parent atom because of electron gain
      • Example: P | P 3-
    • General Trend = increases to left and down
  • 19. Trend #5 – Electron Affinity
    • The energy change that occurs when a neutral atom gains an electron
    • Different from electronegativity, which measures an atom’s attraction for e- when bonded to another atom
    • General Trend = increases to the right and up
    http://www.mcatpearls.com/master/node180.html
  • 20. The Trends in Summary http://cwx.prenhall.com/bookbind/pubbooks/hillchem3/medialib/media_portfolio/text_images/CH08/FG08_17.JPG
  • 21. From Where Did the Elements Come?
    • ~93 in nature (Np, Pm, Tc – in stars)
    • Nuclear reactions in stars; Ex: H, He
    • Transmutation – a nuclear reaction, where one element changes into another
    • Synthetic (lab created) – by transmutation, using particle accelerators; includes all transuranium elements (from #92 on)