The Why is the Periodic Table important to me?

• The periodic table is the most useful tool to a chemist. • You get to use it on every test. • It organizes lots of information about all the known elements. Pre-Periodic Table …

• …was a mess!!! • No organization of elements. • Imagine going to a grocery store with no organization!! • Difficult to find information. • Chemistry didn’t make sense. Johann Wolfgang Dobereiner

• German (1780-1849) • In 1829 noticed he could organize some elements in to groups of three that had similar characteristics. These were called TRIADS. John Newlands

• British (1837-1898) • He noticed in 1865 if the chemical elements are arranged according to increasing atomic weight, those with similar physical and chemical properties occur after each interval of seven elements. • LAW OF OCTAVES John Newlands

Newlands' claim to see a repeating pattern was met with savage ridicule on its announcement. His classification of the elements, he was told, was as arbitrary as putting them in alphabetical order and his paper was rejected for publication by the Chemical Society.

Russian – 1834-1907 • Put elements in rows by increasing atomic weight. • Put elements in columns by the way they reacted. Lothar Meyer

• German (1830-1895) • In 1870 working off the idea of Newlands organized a periodic table according to element mass. • Both Mendeleev and Meyer arranged the elements in order of increasing atomic mass. • Both left vacant spaces where unknown elements should fit.

So why is Mendeleev called the “Father of the Periodic Table” and not Meyer, or both? Mendeleev...

• stated that if the atomic weight of an element caused it to be placed in the wrong , then the weight must be wrong. (He corrected the atomic masses of Be, In, and U) • was so confident in his table that he used it to predict the physical properties of three elements that were yet unknown – including their atomic masses. (Sc, Ga, Ge) • Though still not quite right – check atomic masses of Ar/K, Co/Ni, Te/I and Th/Pa

Henry Moseley In 1913, through his work with X-rays, he determined the actual nuclear charge (atomic number) of the elements*. He rearranged the elements in order of increasing atomic number.

“There is in the atom a fundamental quantity which increases by regular steps as we pass from each element to the next. This quantity can only be the charge on the central positive nucleus.”

1887 – 1915* * Killed in action in WWI The Current Periodic Table

• Mendeleev wasn’t too far off. • Now the elements are put in rows by increasing ATOMIC NUMBER!!

• The Periodic Law states that the physical and chemical properties of the elements recur in a systematic and predictable way when the elements are arranged in order of increasing atomic number. Glenn T. Seaborg After co-discovering 10 new elements, in 1944 he moved 14 elements out of the main body of the periodic table to their current location below the Lanthanide series. These became known as the Actinide series.

1912 - 1999 Groups…Here’s Where the Periodic Table Gets Useful!! • Elements in the Why?? same GROUPS • They have the same have similar number of valence chemical and electrons. physical • They will form the same properties!! kinds of ions. • (Mendeleev did that on purpose.) • Groups are also called families and form the COLUMNS!! Elements in the same or row DO NOT share physical and chemical properties - necessarily

Hydrogen • Hydrogen belongs to a family of its own. • Hydrogen is a diatomic

(H2), VERY reactive gas. • Hydrogen was involved in the explosion of the Hindenberg. • Hydrogen is promising as an alternative fuel source for automobiles. Alkali Metals • GROUP 1 • Very reactive metals, always combined with something else in nature (like in salt). • Soft enough to cut with a butter knife • Low Density. Low BP/MP. Alkaline Earth Metals

• Group 2 • Reactive metals that are always combined with nonmetals in nature. • Brittle, silvery, high BP/MP, low density Transition Metals • Groups 3-12 • Less reactive harder metals. Most dense. Highest BP/MP. Shiny. Ductile. Malleable. • Includes metals used in jewelry and construction. • Metals used “as metal.” Boron Family

• Elements in group 13 • Solids. Rather Reactive. • Aluminum is the most common metal in the Earth’s crust (more silicon and oxygen). Carbon Family • Elements in group 14 • Contains elements important to life, Earth’s Crust and computers. • Carbon is the basis for an entire branch of chemistry. (Organic Chem) • Silicon and Germanium are important semiconductors. • Elements in group 15 Nitrogen Family • Nitrogen makes up over ¾ of the atmosphere. • Nitrogen and phosphorus are both important in living things. • Most of the world’s nitrogen is not available to living things. • The red stuff on the tip of matches is phosphorus. Oxygen Family or • Elements in group 16 • Oxygen is necessary for respiration, oxidation and COMBUSTION. • Many things that stink, contain sulfur (rotten eggs, garlic, skunks,etc.) Halogens

• Elements in group 17 • Very reactive, volatile, diatomic, nonmetals • Always found combined with other element in nature • Low density. Low BP/MP. Brittle solids. The Noble Gases • Elements in group 18 • VERY unreactive, monatomic gases • Used in blimps to fix the Hindenberg problem. And store reactive metals or melt reactive metals. • Have a full valence shell.