THE PERIODIC TABLE (Chapter 6)

Organizing the Elements A few elements, including copper, silver, and gold, have been known for thousands of years There were only 13 elements identified by the year 1700 Chemists began to use scientific methods to search for elements, the rate of discovery increased In one decade (1765–1775), chemists discovered five new elements

J. W. Dobereiner, published a classification system –The known elements were grouped into triads A triad is a set of three elements with similar properties Early chemists used the properties of elements to sort them into groups

Mendeleev arranged elements with…. similar properties in the same row (organized by atomic mass)

The problem wasn’t with the atomic masses but with using atomic mass to organize the periodic table Mendeleev placed tellurium before iodine in his periodic table

Today’s Periodic Table In the modern periodic table, elements are arranged in order of increasing atomic number (number of protons in the nucleus)

Properties of the elements within a period change as you move across a period from left to right. Pattern of properties within a period repeats as you move from one period to the next Elements that have similar chemical and physical properties end up in the same column in the periodic table

Metals, Nonmetals, Metalloids

Metals –Good conductors of heat and electric current –Freshly cut piece of metal is luster (shiny) –All metals are solid at room temperature except Mercury (Hg) –Malleable and ductile Nonmetals –Poor conductors of heat and electric current –Most nonmetals are gases at room temperature (main components of air—nitrogen and oxygen) –A few are solids (sulfur and phosphorus), Bromine (Br) is a liquid –Brittle Metalloids –Properties similar to those of metals and nonmetals (depending on conditions) –Silicon is used in computer chips

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What information can be learned about the elements on the periodic table? Drivers license tell us information…..Name, eye color, height, weight, address, date of birth (unique to each individual)

What Information can we get about an element?

SOLIDS, LIQUIDS, GASES Solids chemical symbol is in black Gases chemical symbol is in red Liquids chemical symbol is in blue **Could be three different colors on a different periodic table (these colors are in reference to the ones in your textbook)

The elements in Group 1 are called alkali metals The elements in Group 2 are called alkaline earth metals. Groups/Families of the Periodic Table

The nonmetals of Group 7 are called halogens The nonmetals of Group 8 are called Noble Gases

Transition Elements Transition metals Displayed in the main body of the periodic table Copper, silver, gold, and iron are transition metals Characterized by the presence of electrons in d orbitals. Inner transition metals Appear below the main body of the periodic table Characterized by the presence of electrons in f orbitals(4f & 5f)

Representative Elements Elements in Groups 1A through 7A (s and p blocks) are often referred to as representative elements They display a wide range of physical and chemical properties.