History of Periodic Table and Periodic Trends

Here are some facts that you should remember about the history of the periodic table~

John Newlands discovered the law of octaves which states that every eighth element shared a common set of properties.

A breakthrough came when Dmitri Mendeleev organized the elements according to mass and their properties. As elements were listed according to mass, certain properties recurred periodically. Mendeleev also broke the periodic table into rows called periods and columns called groups or families.

According to properties, he suspected that there were other undiscovered elements and left gaps for those on his periodic table. Although the current periodic table is organized according to atomic number, Mendeleev provided a big improvement in organizing the periodic table.

The Periodic Law = Properties of the chemical elements recur periodically when elements are arranged from lowest to highest using atomic number.

Here is a cheerful element song! See how many elements you can make out.

• Alkali metals: first group down the periodic table
• Alkaline Earth metals: second group down the periodic table
• Halogens: the seventeenth group down the periodic table
• Noble Gas: The group on the farthest right of the periodic table
• Lanthanides – first row shown under periodic table
• Actinides – the row of elements under the lanthanides

Lanthanides and Actinides are part of the inner transition metals.

Density Graph

Definition: a physical property of matter that describes the ratio of mass to volume

Trend moving down: increase

Trend moving across: decrease

Melting and Boiling Point

Definition: the temperature at which a liquid boils/a solid melts

Trend moving down: there is no obvious trend

Trend moving across:  it is a shifting pattern with the metals and metalloids having increasing melting and boiling point while the non-metals have decreasing points

Ionization Energy

Definition: the amount of energy required to remove an electron

Trend moving down: decrease

Trend moving across: increase

Electronegativity

Definition: the tendency of an atom to attract electrons in the formation of an ionic bond

Trend moving down: decrease

Trend moving across: increase

Atomic Radius

Definition: a measure of the size of an element, the distance from the nucleus to the boundary of the surrounding cloud of electron

Trend moving down: increase

Trend moving across: decrease