The Periodic Table Arranging the Elements Trends n

The Periodic Table Arranging the Elements

Trends n Trend = pattern What trends to you see from right to left? n What trends to you see from top to bottom? n

n Right to Left n n n the body of each character in each row is the same shape as you move there is a finger added each time Top to Bottom n n n In the first two columns, as you move down another hair is added to the head In the third column, the feet get longer In the fourth column, there is an additional line added in the body

To Review: Finding Your Way Around the P. T. n n n Period = row (across) Group = column (down) Like coordinates on a grid

Actual Shape of the Periodic Table If the Lanthanides and Actinides are put in the table and not left underneath

Group = Column

Period = Row

Mendeleev’s Periodic Table n n n 1860’s: Mendeleev ordered elements by atomic mass Predicted properties of unknown elements based on properties of surrounding elements But some elements were still out of place—he thought his calculations were wrong

What element is it? Atomic Mass Density Appearance Melting Point Mendeleev’s Actual Properties Predictions 72 72. 6 5. 5 g/cm 3 5. 3 g/cm 3 Dark gray metal Gray metal High melting pt 937 C The unknown element turned out to be Germanium

Proton Discovered 1914—Proton discovered and understood n British scientist Henry Moseley arranged elements based on atomic number n

n n n Periodicity Element properties show “periodicity”—regular, repeating pattern Since 1914 more elements have been discovered All follow the periodic law: chemical and physical properties of elements are periodic functions of their atomic number

Periodicity of Density

Metallic Character

Atomic Radius n n Trend across a period? Trend down a group?

Reactivity n n Reactivity (how intensely an element reacts with other substances) Elements react by taking, giving, or sharing electrons to get a full shell

Melting Point n n Metals: basically decrease down the group Non-metals: basically increase down the group

Density

Spiral Periodic Table