Unit #4: Periodic Table Chapter 5

The Periodic Table Origin of the Table Origin of the Table 1. J.W. Dobereiner (early 1800’s) German a. observed that several elements could be organized into groups of three- called “triads” b. elements of each triad shared similar properties

2. J.A.R Newlands (1865)- English a. arranged table according to atomic mass b. observed periodicity of the elements c. law of octaves: properties of elements repeat every eighth element

3. Dmitri Mendeleev (1869)- Russian a. Published first table that is the basis for today’s periodic table b. arranged elements by increasing atomic mass c. assigned elements with similar properties to the same columns d. predicted existence of missing elements based on his table e. problem: some elements did not fit according to their atomic mass and properties - I / Te - Co / Ni - Ar / K

4. H.G.J. Moseley (1913)- English a. developed idea of atomic number b. used x-rays to determine the atomic number of elements c. corrected Mendeleev’s table by arranging elements according to atomic number, not atomic mass d. founded modern periodic law: when elements are arranged in order of increasing atomic number, their physical and chemical properties show a periodic pattern

B. Reading the Table 1. Be familiar with the location of: a. Alkali metals b. Alkaline earth metals c. Metalloids d. Transition metals e. Nitrogen family f. Oxygen family g. Halogens h. Noble gases i. s, p, d, f blocks j. Horizontal rows- period or series k. Veritcal columns- group or family l. Most probable charge and outer shell configuration

C. Periodic Trends 1. Atomic Radius a. the distance from the center of an atom’s nucleus to its outer most electron decrease increase Decrease – Left  Right Increase – Top  Bottom

2. Ionic Radius a. no clear trend b. take in electron - ionic radius increases - + charged nucleus is attracting more electrons - full outer shell results in increased repulsion among electrons c. remove electron - ionic radius decreases - + charged nucleus is attracting fewer electrons

3. Ionization Energy a. Energy required to move an electron increase Increase – Left  Right Top  Bottom

4. Electronegativity a. an atom’s ability to attract electrons in a chemical bond increase Increase – Left  Right Top  Bottom