The Periodic Table and Periodicity notes by stariya

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									The Periodic Table and Periodicity
I. History of Development
A. Antoine Lavoisier – French – late 1790s
1. Compiled list of 23 elements known at the time
2. changes in world
a. electricity
b. spectrometry
c. industrial revolution
B. Stanislao Cannizzaro - Italian – 1860
1. International Congress of Chemists in Germany
2. method for accurately measuring atomic mass
C. John Newlands – English - 1864
1. Law of octaves –every 8th element had repeating pattern when arranged by increasing
            atomic mass
2. Did not work for all elements
D. Lothar Meyer – German – 1869
E. Dmitri Mendeleev – Russian – 1869
 1. organized 60+ known elements by atomic mass and other                      properties
2. 1871 - predicted properties of 3 unknown elements
3. By 1886 - Sc, Ga, Ge found with predicted properties
               -But, a few elements did not seem to fit in correct group
F. Henry Mosely - 1911-1913
 1. analyzed spectra of 38 metals to find nuclear charge (#p +)
2. rearranged periodic table by atomic number
       G. As other scientists found the existance of the noble gases & inner
               transition metals, they were added to PT
Basic PT organization
A.     Main divisions
1. Metals
       a. transition metals
       b. inner transition metals
                       c. lanthanide series
d. actinide series
2. nonmetals
3. metalloids/semi-metals
representative elements
       B. Group (family) names - vertical columns
       group # = # of valence e- except for transitions
1.             alkali metals
2.             alkaline earth metals
3.             halogens
4.             noble gases
C. Periods - horizontal rows
               period# = # of principal energy levels
Numbering system
A and B
1-18

IV. Electron Configuration
A.   s-block elements
1.              alkali metals
2.              alkaline earth metals
3.              filled/partially filled s orbitals
B. p-block elements
1.              filled/partially filled p orbitals
2.              noble gases incredibly stable due to filled s & p orbitals
C.      d-block elements
1. filled outermost s and filled/partially filled nearby d orbitals
D. f-block elements
        1. lanthanide & actinide series
2. do not fill orbitals in a predictable manner
3. filled/partially filled outermost s and filled/partially filled 4f or 5f

Example questions
Without using the periodic table, determine the following:
Determine the group, period, and block of the following e-config.
[Ne]3s2
 [He]2s2
[Kr]5s24d105p5
Write the e- config for the following elements:
the group 2A element in the fourth period
the noble gas in the fifth period
the group 6A element in the second period

3. What are the symbols for the elements with the following valence e- configs?
s2d1
s2p3
s2p6

Periodic Trends
A.     atomic radius
1.           define: one-half the distance between adjacent nuclei
2.           periodic trend: decreases as you go across a period due to
             increasing positive nuclear charge with no additional shielding
             effect
3.           group trend: increases as you move down a group due to
             increasing principal energy levels with an increased shielding effect
             on the increased nuclear charge
B.     ionic radius
define: radius of positive or negative ion
positive ions: always smaller than neutral atom due to increased nuclear charge
               and empty outer orbital
negative ions: always larger than neutral atom due to increased electrostatic
               repulsion
4. periodic trend: decreases as you move across a period
 group trend: increases as you move down a group

C. ionization energy - 1st, 2nd, 3rd, etc
1.             define: energy required to remove an electron from a gaseous
              atom (an indication of how strongly an atom holds onto its valence
              electrons
2.            periodic trend: increase as you move across a period due to
              increased nuclear charge
3.            group trend: decrease as you move down a group due to
              increased shielding effect and greater distance from nucleus

D. Electronegativity
define: relative ability of an atom to attract electrons in a chemical bond
periodic trend: increases as you move across a period due to increased nuclear
               charge
group trend: decrease (stay the same) as you move down a group due to
               increased shielding effect

Electron Affinity
define: energy change that occurs when an electrton is acquired by a neutral
              atom
positive number: energy absorbed – leads to unstable nucleus – electron lost
              spontaneously
negative number: energy released – leads to more stable nucleus – electron
              kept
periodic trend: become increasingly negative as you move across a period
              (halogens are most EN)(Fluorine is most chemically active
              nonmetal)
group trend: become increasingly positive as you move down a group due to
              increased shielding effect.

								
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