Chapter 6 The Periodic Table Ch. 6.1 Organizing the Elements

Searching For an Organizing Principle Only 13 elements identified by Discovery of elements increased with use of scientific method. Chemists used the properties of elements to sort them into groups. Groups were organized according to similar properties.

Mendeleev’s Periodic Table In 1869, Demitri Mendeleev published a periodic table of the elements. He arranged the elements in his periodic table in order of increasing atomic mass. He left blank spots in his table and predicted missing elements, which were in fact later found.

The Periodic Law In the modern periodic table, elements are arranged according to increasing atomic number. 7 rows, or periods, in the table, corresponding to a principle energy level. The elements within a column have similar chemical properties. The pattern of properties within a period change as you move across a period from left to right.

Periodic Law: When elements are arranged in order of increasing atomic number, there is a periodic repetition of chemical and physical properties.

Three Classes of Elements: Metals, Nonmetals, and Metalloids Metals—about 80% of elements. Good conductors of heat and electricity. High luster or sheen on freshly cut or cleaned surface. Solids at room temperature, except mercury. Many are ductile; most are malleable.

Nonmetals Upper-right corner of periodic table. More variation in physical properties than metals. Most are gasses at room temperature. Bromine is a liquid. Poor conductors of heat and electricity, with exception of carbon. Brittle.

Metalloids Elements on the boundary between metals and nonmetals. Properties similar to both metals and nonmetals, depending on conditions. Changing the conditions often changes the properties of metalloids.