Classification of Elements The Periodic Table

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The Wonders of the Periodic Table

Just in case you are ever on Jeopardy…. The first recorded scientific discovery of an element was in 1649 when Hennig Brand (German) discovered Phosphorous (atomic number 15). As the number of known elements grew, scientists began to recognize patterns in properties and began to develop classification schemes.

Arranging the Elements Dmitri Mendeleev (1887), a Russian scientist, looked at the chemical and physical properties of elements and organized them on the basis of their similarities By arranging the 63 known elements, he found that by placing them by increasing atomic weight he could put them into 7 groups, or columns. He found the pattern, all the elements in a column have the same valences, the number of electrons in the outer shell

The Modern Periodic Table British scientist, Henry Mosley, arranged the elements according to their atomic number The Periodic Law states that the physical and chemical properties of the elements are periodic functions of their atomic number

Design of the Periodic Table Classification system used to organize all the elements Information can be obtained about each element just by where it is placed in the periodic table!

Columns Called groups or families Have similar, but not identical properties

Rows Also called periods Elements are not alike in the rows First element in a row is an extremely active solid, where as the last is always an inactive gas There are 7 periods, with period 6 separated out to make the periodic table shorter Each of the rows fills the same electron orbits

Columns and Rows

Element Key, each element has their own…….

It is just the beginning!!!!

Let’s look at what we have…

Most of the 109 elements are classified as metals Physical properties : Luster or shininess Ductile means made into thin wires Malleable means hammered into thin sheets Allows heat and electricity to pass through Have a high density

Chemical Properties of Metals Depends on the number of electrons in the outer shell of the atom These outer shell electrons are weakly held and tend to be lost when they chemically combined Easily react with water and gases in the atmosphere Metals are corrosive, they wear away ex. rust and tarnish

Position of Elements

Nonmetals Physical properties are opposite of metals, they are dull, brittle, and break easily, they are not ductile or malleable, and they can be a solid, liquid, or a gas Chemical properties are determined by the number of electrons in their outer shell Last row has 8 electrons in their outer shell, so they are non reactive

Metalloids They have properties of both metals and nonmetals Metal-like They conduct heat and electricity, but not as well as metals Can be shiny or dull Are ductile and malleable Include; boron, silicon, germanium, arsenic, antimony, tellurium, polonium, and astatine

And to think: this is only the beginning………..