Periodic Table

Dmitri Mendeleev (1837 – 1907) In 1869 Mendeleev and Lothar Meyer (Germany) published nearly identical classification schemes for elements known to date. The periodic table is base on the similarity of properties and reactivities exhibited by certain elements. Later, Henri Moseley ( England, ) established that each elements has a unique atomic number, which is how the current periodic table is organized.

Horizontally into Periods

The period 4 atoms each have 4 electron containing shells K (Potassium)Fe (Iron)Kr (Krypton) 4 th Shell (n = 4)

Vertically into Groups

Each group has distinct properties  The periodic Table is divided into several groups based on the properties of different atoms

The Group 2 atoms all have 2 electrons in their outer shells

 Soft, silvery coloured metals  Easy to cut with knife  Have low densities – All float on water  Never found free in nature  Very reactive Alkali Metals

 Slowly react with oxygen to form oxide  Burn rapidly when heated in oxygen  Produce coloured flames Alkali Metals reacting with oxygen Lithium + Oxygen  Lithium oxide Sodium + Oxygen  Sodium oxide Potassium + Oxygen  Potassium oxide

Li (Lithium) Na (Sodium) K (Potassium) Alkali Metals reacting with water

 React with water to form hydroxide and hydrogen gas Alkali Metals reacting with water Lithium + Water  Lithium hydroxide + H 2 Sodium + Water  Sodium hydroxide + H 2 Potassium + Water  Potassium hydroxide + H 2

Alkali Metals uses Lithium is used to make alloys and is an anode material for batteries. Used as medication for bipolar disorders. Potassium is used in fertilizers. Sodium is used in the food industry as sodium chloride or table salt (NaCl) and is used in street lighting to produce a soft orange glow.

Alkaline Earth Metals Silvery-White Metals Fairly reactive Many are found in rocks in the earth’s crust

Most are Poisonous Fairly reactive Halogens

Unreactive Gases at room temperature Noble Gases

Jellyfish lamps made with noble gases

He (Helium): pale peach Ne (Neon): orange-red Ar (Argon): pale lavender Kr (Krypton): pale silver Xe (Xenon): pale, deep blue Colours noble gases produce in lamp tubes:

Transition Metals Malleable (easily bent/hammered into wires or sheets) Most are good conductors of electricity

Metalloids lie on either side of these “stairsteps” They share properties with both metals and non-metals Si (Silicon) and Ge (Germanium) are very important “semi-conductors”

What are semiconductors used in?

Nonmetals Brittle Do not conduct electricity

Lanthanide Series Actinide Series