Elements and The Periodic Table

Classification of Matter

“I Have No Bright Or Clever Friends” The 7 Diatomic Elements “I Have No Bright Or Clever Friends” Or… HOFBrINCl

Dimitri Mendeleev 1869 Credited as the Father of the Periodic Table Periodic Law: When arranged by atomic number, the properties of the elements repeat at regular intervals.

Mendeleev heard about atomic masses He placed the name of each known element on a card, together with the atomic mass of the element and a list of observed chemical and physical properties. He then arranged the cards according to various properties and looked for trends or patterns.

Mendeleev noticed that when the elements were arranged in order of increasing atomic mass, certain similarities in their chemical properties appeared in regular intervals. Such a repeating pattern is referred to as periodic. Mendeleev created a table in which elements with similar properties were grouped together – a periodic table of elements! His procedure of organizing according to atomic mass left several empty spaces in his table and he was able to predict the properties of the elements that would fill these spaces!

Henry Mosely In 1911, Henry Mosely discovered that the elements in the periodic table fit into patterns better when they were arranged in order of increasing atomic number. Periodic Law states that the physical and chemical properties of the elements are periodic functions of the atomic numbers.

The periodic table has undergone extensive changes since Mendeleev’s time. Chemists have discovered new elements and, in more recent years, have synthesized new elements. The periodic table is an arrangement of the elements in order of their atomic numbers so that the elements with similar properties fall into the same column, or group.

Long Form of the Periodic Table

and the same number of valence electrons

Metals, Non-metals, and Metalloids There are two basic divisions on the periodic table. A thick zigzag line on the right-hand side on the periodic table designates the division. Elements to the right of the line are non-metals, while the elements to the left are the metals (including the lanthanide and actinide series). Elements along the border between metals and no-metals are called the metalloids. These exhibit properties of both metals and non-metals.

Metals, Non-metals, and Metalloids

Metaloids Contains properties of both metals and non-metals Silicon Physical Properties Shiny or Dull Malleable Ductile Solid at room temperature Properties Better conductor than non-metals but worse than metals Better conductors at high temperatures Polonium is radioactive Silicon Arsenic Germanium

Hydrogen (A class of it’s own) Sometimes it behaves like an alkali metal, sometimes like a halogen, and sometimes in its own unique way.

Group 1: Alkali Metals 1 valence electron (electrons in their outermost shell) Soft, shiny, easily cut with a knife The most reactive metals React violently with water (stored in oil or a vacuum) React with halogens to form salts Never found as free elements in nature, always bonded with other elements Braniac: alkali metals Disposal of sodium 1947

Group 2: Alkaline Earth Metals 2 valence electrons Light, reactive metals Form oxides when exposed to air. React with oxygen to from oxides, react with hydrogen to form hydrides (except beryllium). React with water to liberate hydrogen

Groups 3-12: Transition Metals 1 or 2 valence electrons Strong, hard metals Good conductors of heat and electricity Wide range of chemical and physical properties

Group 17: Halogens 7 valence electrons Extremely reactive nonmetals Not lustrous, nonconductors of electricity

Group 18: Noble Gases Full outer shell Extremely unreactive (inert)

Lanthanides (Rare Earth Metals) Elements 57-70

Actinides Elements 89-102 Transuranic Elements: Synthetic elements