Development of the Periodic Table

Chapter 5 Part 1

The Periodic Table• By the mid 1800’s

about 70 elements had been identified.

• There was not yet a system to organize them.

• Early attempts looked at some of the similarities but were not complete.

Mendeleev: Father of the Periodic Table

• Meyer also came to the same conclusion, but Mendeleev got the credit.

Table                                               

The Modern Periodic Table

• Mosley took the Mendeleev and Meyer’s idea one step further. They had arranged the table based on the elements’ atomic mass.

• Mosley discovered how to find out the elements’ number of protons using X-rays.

• The modern periodic table is arranged by atomic number, the number of protons.

How to Read the Periodic Table• Top number is the

Atomic Number. It is the number of protons which equals the number of electrons

• The bottom number is the Atomic Mass. The average number of Protons and Neutrons in an element.

Good sources on the Web.

• For further reading and cool graphics on the periodic table (and also where I got most of my images for this presentation:

• http://mooni.fccj.org/~ethall/period/period.htm

• Another fun site:• http://

www.privatehand.com/flash/elements.html

Two New Elements                   

WOMANIUM (WO) Physical properties: Generally soft and round in form. Boils at nothing and may freeze any time. Very bitter if not used well. Chemical properties: Very active and highly unstable. Possesses strong affinity with gold, silver, platinum, and precious stones. Violent when left alone. Turns slightly green when placed next to a better specimen. Usage: An extremely good catalyst for dispersion of wealth. Caution: Highly explosive in inexperienced hands!

New ElementsMANIUM (XY)

Physical properties: Solid at room temperature but gets bent out of shape easily. Difficult to find a pure sample. Due to rust, aging samples are unable to conduct electricity as easily as young samples. Chemical properties: Attempts to bond with WO any chance it can get. Also tends to form strong bonds with itself. Becomes explosive when mixed with Childrium for prolonged period of time. Usage: Possibly good methane source. Caution: In the absence of WO, this element rapidly decomposes and begins to smell.