Periodic Table Arranging Elements

The Pattern -1860's: Russian chemist, Dmitri Mendeleev studies elements -discovers that elements are periodic , they follow a regular, repeating pattern based on increasing atomic mass -recognizes similar physical and chemical properties in every 8th element -his arrangement called a "Periodic Table" -also recognized that elements were missing from his table -used pattern to predict existence and properties of missing -those missing elements have now been discovered

Changing the Arrangement -some elements didn't fit Mendeleev's pattern -1914: Henry Moseley rearranged periodic table by atomic number (the # of protons in one atom of an element) instead of atomic mass -all elements fit new arrangement -all new elements discovered since 1914 also followed this periodic law (the physical and chemical properties of elements are periodic functions of their atomic number) Henry Moseley

Navigating the Table -periodic table contains information that can help you understand it -elements classified as metals, nonmetals, or metalloids -also classified by number of electrons in outer energy level (valence electrons) -zig-zag line identifies metals, nonmetals, and metalloids: Metals - found to left of zig-zag & have few electrons in outer level Nonmetals - found to right of zig-zag & most have a nearly complete set of electrons in outer level Metalloids – border zig-zag line and outer levels are about half complete

Atomic Number Symbol Element Name Atomic Mass -each square contains information about a different element including: Atomic Number Symbol Element Name Atomic Mass

-names and symbols of each element approved by panel of scientists -some elements named for important scientists: mendelevium or einsteinium -others named for geographical regions: germanium or californium -symbols are usually one or two letters (if 1 letter - always capitalized, if 2 letters - 1st capitalized, 2nd lowercase) -5 basic patterns for writing chemical symbols

Patterns for Chemical Symbols Example 1st letter of name S - sulfur 1st 2 letters of name Ca - calcium 1st letter & 3rd or later letter Mg - magnesium letter(s) of word other than English name Pb - lead (from latin plumbum ) 1st letter of root words that stand for the atomic number (used for elements whose official names have not yet been chosen) Uut - ununtrium (for atomic # 113)

Period Group -rows of periodic table called periods -properties in each row follow a repeating pattern -physical and chemical properties change gradually (from left to right) as elements change from metals to nonmetals -columns (top to bottom) called groups -elements in each group have similar properties -groups also called families Period Group