The Periodic Table Proposed by Mendeleev

Dmitri Ivanovich Mendeleev 1834-1907 Born in Siberia, the last of at least 14 children, Dmitri Mendeleev revolutionized our understanding of the properties of atoms and created a table that probably adorns every chemistry classroom in the world.

Arrangements Periods – Rows – determines the number of energy levels in an atom Lanthanide Series (57-71) – rare earth elements Actinide Series (89-109) – radioactive elements

Lanthanide Series – Rare Earth Elements                                                                         Not as rare as once thought The lanthanides have many scientific and industrial uses. Their compounds are used as catalysts in the production of petroleum and synthetic products. Lanthanides are used in lamps, lasers, magnets, phosphors, motion picture projectors, and X-ray intensifying screens.

Cerium Lanthanum

Actinide Series - Radioactive                                                       They are all radioactive and some are not found in nature. Some of the elements with higher atomic numbers have only been made in labs.

Arrangements (cont.) Groups or Families – arranged according to the number of electrons in the outer energy level IA or 1 – alkali metals IIA or 2 – alkali earth metals VIIB or 17 – halogens VIII or 18 – noble gases – inert gases

Alkali Metals Very reactive One electron in the outer shell Shiny                                                      . Very reactive One electron in the outer shell Shiny Light weight

Sodium

Alkaline Earth Metals Two electrons in the outer shell                                                       So we just                                                      . Two electrons in the outer shell Fairly reactive (not as reactive as Alkali metals

Magnesium - Mg Magnesium tarnishes slightly in air, and finely divided magnesium readily ignites upon heating in air and burns with a dazzling white flame. Normally magnesium is coated with a layer of oxide, MgO, that protects magnesium from air and water.

The Halogens                                                     They have seven electrons in their outer shell. They are all just one electron shy of having full shells. Because they are so close to being “happy”, they have the trait of combining with many different elements. You will often find them bonding with metals and elements from Group One of the periodic table.

Halogens The Halogens are a generally nasty bunch. Think toxic choking fumes. But in compounds with the similarly strong-willed alkali earths, they can be delicious. Fluorine F

Inert Gases - Noble Gases                                                    All of the inert gases have full outer shells with eight electrons. Oh wait! That's not totally correct. At the top of the inert gases is little helium (He) with a shell that is full with two electrons. The fact that their outer shells are full means they are quite happy not reacting with other elements.