Organizing the Periodic Table

What is a periodic Table? A periodic table is an arrangement of elements that explains and predicts physical and chemical properties.

How is the periodic table organized? Mendeleev came up with the best arrangement for the elements on the periodic table. He decided to arrange the elements by increasing atomic mass. He discovered that by organizing the elements in this way, that some elements had similar properties as other elements.

Mendeleev’s Periodic Law If the elements are arranged according to their atomic mass, a pattern can be seen in which similar properties occur regularly.

A closer look at the periodic Table

All the elements in a column on the table are called a chemical group. These elements have similar physical and chemical properties. These elements also form similar kinds of compounds when they combine with other elements.

The elements that are found side-by-side show similar properties and gradual changes in these properties. These horizontal rows are called periods. As you move from left to right in a row the atomic number increases and the elements change from metals to nonmetals to the noble gases.

Hydrogen Hydrogen is in a group of its own because it is unique to all other elements on the periodic table. Hydrogen has the ability to react like a metal as well as a non-metal. Hydrogen exists in combinations with other elements.

Alkali Metals The first column of elements on the periodic table is referred to as the alkali metals. These elements are all shiny, silvery metals that are extremely reactive. Because they combine so easily with other elements they are only found in nature in the form of a compound.

Metalloids Elements that have both metallic and nonmetallic properties are called metalloids. These are the elements that make up the staircase on the periodic table.

Transition Metals Elements in groups 3-12 Less reactive harder metals Includes metals used in jewelry and construction. Metals used “as metal.”

Halogens Fluorine, chlorine, bromine and the other halogens occupy the 17 th column on the periodic table. The halogens are the most reactive non- metals and they almost always appear in nature in the form of a compound.

The Noble Gases The last column of elements on the periodic table is referred to as the noble gases. These gases are unreactive and almost never form compounds with other elements.