The Periodic Table

REVIEW All atoms of a specific element are alike All atoms of different elements are different 90 naturally occurring Arranged on Periodic Table to show trends

A Brief History of the Periodic Table Mendeleev – Moseley - Seaborg

Mendeleev (1869) Thought pattern must exist between all elements Organized table by... ATOMIC MASS Elements in columns show similar properties… Both physical and chemical! Predicted properties of “missing” elements

Mendeleev’s TABLE His notes

What he thought! “I began to look about and write down the elements with their atomic weights and typical properties, analogous elements and like atomic weights on separate cards, and this soon convinced me that the properties of elements are in periodic dependence upon their atomic weights.” Mendeleev, Principles of Chemistry, 1905, Vol. II as quoted at <http://www.aip.org/history/curie/periodic.htm>.

Definition What does PERIODIC mean? A repeating pattern Mendeleev left some spaces in his table because not all elements lined up according to atomic mass. He used info he knew about surrounding elements to PREDICT properties and masses of unknown elements. How about that!

Mendeleev’s Predictions vs. Actual Properties of Element # 32   “Ekasilicon” Germanium Date 1871 (predicted) 1886 (discovered) Atomic Mass 72 72.6 Density 5.5 g/cm3 5.47 g/cm3 Bonding power 4 Color Dark gray Grayish-white

Moseley (c. 1914) rearranged table by ... ATOMIC NUMBER determined atomic number of elements by using x-rays to determine number of protons in element

Moseley’s work

Seaborg (1944) rearranged Periodic Table with... Lanthanide and Actinide Series pulled out/separated from main Periodic Table discovered 10 new elements & countless isotopes

3D Alexander’s Arrangement of Elements

definition Periodic Law The physical and chemical properties of the elements are periodic functions of their atomic number

definition Octet Rule The tendency of atoms to gain or lose electrons so they acquire eight electrons in their outer energy level

Columns of Table = groups or families Numbered 1 – 18 Group numbers tell us the number of electrons in that element’s outer energy level - the number in red Elements within the same family have similar but not identical properties 16 18 1 2 15 17 14 13

definition Valence electrons electrons found in the outermost energy level use the group number (the number in red) to determine number of valence electrons

NAMES to Know

NAMES to Know Group 1 Alkali Metals

NAMES to Know Group 2 Alkaline Earth Metals

NAMES to Know Groups 3-12 Transition Metals

NAMES to Know Inner Transition Metals: Lanthanide Series Actinide Series

NAMES to Know Group 16 Chalocgens

NAMES to Know Group 17 Halogens

NAMES to Know Group 18 Noble Gases

Rows of Table = periods 7 periods Period = # of energy shells in atom Properties are not alike within a period: across each period (row), the chemical & physical properties of elements change these properties are repeated in the next period (the row below)

Periods 1 to 7 1 2 3 4 5 6 7

Regions of the Periodic Table Metals - to the left of the stair-step line Non-Metals - to the right of the stair-step line Metalloids - along the stair-step line

Regions of the table One more! NONMETALS METALLOIDS METALS

Metals Found to LEFT of zigzag line on table Good conductors of heat & electricity Malleable Ductile High melting points Shiny Tend to lose electrons  forming cations

Nonmetals Found to RIGHT of zigzag line on table Plus Hydrogen (atomic number = 1) Poor conductors of heat & electricity Brittle when solid Dull Low melting points Tend to gain electrons  forming anions

Metalloids aka Semi Metals Found along both sides of zigzag line Properties of both metals & nonmetals Okay conductors of heat & electricity Shiny or dull