The Periodic Table Woo Hoo!

Why is the Periodic Table important to me? The periodic table is the most useful tool to a chemist. It organizes lots of information about all the known elements.

Pre-Periodic Table Chemistry … …was a mess!!! No organization of elements. It looked like my attic - stuff everywhere in no particular order. Difficult to find information. Chemistry didn’t make sense.

Dmitri Mendeleev: Father of the Table WHAT HE DID… Put elements in order of increasing ATOMIC MASS. (1869) Shifted the rows under each other to make columns of similarly reacting elements Something wasn’t right…. He left blank spaces for what he said were undiscovered elements. He broke the pattern of increasing atomic weight to keep similar reacting elements together.

The Current Periodic Table Mendeleev wasn’t too far off. Mosley (1914) created the modern periodic table by putting the elements in rows by increasing ATOMIC NUMBER!!

How is it organized? Non-metals Metalloids Metals

Properties Metals: Non-metals: Strong Brittle Malleable and ductile Brittle React with oxygen to form basic oxides React with oxygen to form acidic oxides Sonorous Dull sound High melting and boiling points Low melting and boiling points Good conductors of electricity Poor conductors of electricity Good conductors of heat Poor conductors of heat Mainly solids at room temp. Solids, liquids and gases at room.temp. Shiny when polished Dull looking When they form ions, the ions are positive When they form ions, the ions are negative - except hydrogen that forms a positive ion, H+. High density Low density

…and… The horizontal rows are called periods and are labeled from 1 to 7. 1234567

…and… The vertical columns are called families or groups and are labeled from 1 to 18. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Groups…Here’s Where the Periodic Table Gets Useful!! Elements in the same group have similar chemical and physical properties!! (Mendeleev did that on purpose.) Why?? They have the same number of valence electrons. They will form the same kinds of ions.

Families on the Periodic Table Families have names rather than numbers. (Just like your family has a common last name.) Example: column 1 is the Alkali Metals family They have similar properties. (Grandma’s crazy, Dad’s crazy, the son’s crazy..)

Hydrogen - Oddball #1 Hydrogen sometimes behaves like a column 1 family and sometimes like a column 7 familiy. Thus it belongs to a family of its own. Often placed at the top center of periodic table Hydrogen is a diatomic, reactive gas. Hydrogen was involved in the explosion of the Hindenberg.

Helium - Oddball #2 Helium has the wrong number of valence electrons to be in group 18. However, it behaves that way, so that’s where it is grouped.

Alkali Metals 1st column on the periodic table (Group 1) not including hydrogen. Very reactive metals, always combined with something else in nature (like in salt). Soft enough to cut with a butter knife Explodes in water

Alkaline Earth Metals Second column on the periodic table. (Group 2) Not as reactive as column 1 metals, but still fairly active chemically. Not found alone in nature, always combined Family includes mineral nutrients (calcium, magnesium)

Transition Metals Elements in groups 3-12 Less reactive, harder metals Very conductive (heat and electricity) Combine easily with oxygen to make oxides Make brightly colored componds. Metals used “as metal.”

Boron Family Elements in group 13 Contains a metalloids, boron Aluminum metal was once rare and expensive, not a “disposable metal.”

Carbon Family Elements in group 14 With 4 valence electrons it is a very versatile elements - can make lots of combinations. Carbon is the basis of all living things. Silicon is the most abundant mineral in the earth’s crust.

Nitrogen Family Elements in group 15 Family includes metal nonmetals and metalloids Nitrogen makes up about 70% of the atmosphere. Nitrogen and phosphorus are both important in living things. The red stuff on the tip of matches is phosphorus.

Oxygen Family or Chalcogens Elements in group 16 Made of metals, nonmetals and metalloids Oxygen is necessary for respiration. Many things that stink, contain sulfur (rotten eggs, garlic, skunks,etc.)

Halogens Elements in group 17 Very reactive, volatile, low melting and boiling points; in gas form are diatomic Nasty, toxic fumes when solo Fortunately always found combined with other element in nature . Halogens combine readily with metals to form a class of compounds known as salts.

The Noble Gases Elements in group 18 VERY unreactive, gases Colorless gases used in lighted “neon” signs Used in blimps to fix the Hindenberg problem. Have a full valence shell.