Periodic TableArranging Elements

The Pattern-1860's: Russian chemist, Dmitri Mendeleev studies elements-discovers that elements are periodic 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 elements-those missing elements have nowbeen discovered

Changing the Arrangement-some elements didn't fit Mendeleev's pattern-1914: Henry Moseley rearranged periodic table by atomicnumber (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 lawperiodic 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 electronsvalence electrons)-zig-zag line identifies metals, nonmetals, and metalloids:

Metals - found to left of zig-zag & have fewelectrons in outer levelNonmetals - found to right of zig-zag & most have a nearly complete set of electrons inouter levelMetalloids – border zig-zag line andouter levels are about half complete

-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 SymbolsPattern Example

1st letter of name

1st 2 letters of name

1st letter & 3rd or later letter

letter(s) of word otherthan English name

1st letter of root wordsthat stand for the atomicnumber (used for elementswhose official nameshave not yet beenchosen)

S - sulfur

Ca - calcium

Mg - magnesium

Pb - lead (from latinplumbum )

Uut - ununtrium (foratomic # 113)

-rows of periodic table called periodsperiods -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 groupsgroups-elements in each group have similar properties-groups also called families

Period

Group