The Periodic Table Of Elements

Development of the Modern Periodic Table Objectives Trace the development and identify key features of the periodic table Identify specific groups within the periodic table

Organizing by Properties 1869 – Dmitri Mendeleev organized known elements into chart (rows and columns) According to atomic mass Similar to putting together a large puzzle Predicted new elements would be discovered with certain properties

Arranging by Atomic Number Many discrepancies with Mendeleev’s table Moseley arranged by increasing atomic number rather than atomic mass Discrepancies disappeared

Periodic Law The properties of the elements repeat periodically when the elements are arranged in increasing order by their atomic number.

Modern Periodic Table

First Ionization Energy The energy required to remove one electron from an atom in a gaseous phase

Periodic Table Today Vertical column = group or family Horizontal row = period Check out periodic table on wall

Chemical Families 1A = alkali metals (react with water to form alkaline, or basic, solution 2Na(s) + 2H2O(l) = 2NaOH(aq) + H2(g) + heat energy 2A = alkaline earth metals also react with water 7A = halogens (salt formers)\ 1A-8A = representative metals Bgroup (2A-3A) = transition metals Two bottom rows = inner transition metals (lanthanides and actinides)

Periods 7th period incomplete – fewer than half occur naturally on earth and all are radioactive

Classification Cont. Metals – to the left of the staircase Properties: generally shiny when smooth and clean, solid at room temperature, good conductors of heat and electricity Nonmetals – to the right of the staircase Properties: generally gases or brittle, dull-looking solids. Poor conductors of heat and electricity Metalloids – bordering staircase Si and Ge are most important for use in semiconductors

Homework 6.1 assessment P.174 # 26-40 Quarter extra credit (25 points exam) Develop a periodic table (must be large on posterboard) expressing periodicity in an interest you may have

Activity In the cards periodic table activity