The Periodic Table Physical Science

The Search for Order http://www.youtube.com/watch?v=d0zION8xjbM

The Search for Order Until 1750, scientists had discovered only 17 elements. The rate of discovery of elements began increasing rapidly providing a need for organization.

Search for Order In 1789, Antoine Lavoisier divided the elements into categories of metals, nonmetals, gases, and earths. For the next 80 years, scientists looked for a better method that would include all of the elements.

Scientists of the Periodic Table Antoine Lavoisier Dmitri Mendeleev

Mendeleev’s Periodic Table In the 1860’s, Dmitri Mendeleev found a way to better organize the elements. Mendeleev arranged the elements into rows in order of increasing mass so that elements with similar properties were in the same column.

Mendeleev’s Periodic Table Allowed for the prediction of elements that had not yet been discovered. Mendeleev named missing elements after elements in the same group.

Mendeleev’s Periodic Table Mendeleev named one of his predicted elements eka-aluminum. He predicted it would be a soft metal with a low melting point and have a density of 5.9. The element was later discovered and named gallium.

Mendeleev’s Periodic Table The close match between Mendeleev’s predictions and the newly discovered elements showed the accuracy of his periodic table.

Modern Periodic Table Mendeleev did not know about the existence of protons when he created the periodic table. The modern periodic table has elements arranged by increasing atomic numbers.

The Modern Periodic Table

Modern Periodic Table Each row is a period. Each column is a group.

Periodic Law Properties of elements repeat in a predictable way when atomic numbers are used to arrange elements into groups. (Because elements in groups have similar electron configurations.)

Classes of Elements First: Elements are divided into solids, liquids, or gases based on their states at room temperature.

Classes of Elements Second: Elements are divided into those that occur naturally and those that do not. Elements 1-92 occur naturally 93 and higher do not

Classes of Elements Third: Elements are divided into categories based on their general properties. Metals Nonmetals Metalloids

Metals Elements that are good conductors of electric current and heat. The majority of elements on the periodic table are metals.

Metals Except for Hg, metals are solid at room temp. Most metals are malleable. Some metals are reactive and some do not react easily.

Transition Metals The elements in groups 3-12. They bridge the elements on the left and right sides of the table. Transition metals have similar properties to one another, and can be used to form compounds of distinctive colors.

Nonmetals Have properties opposite to that of metals. (They are poor conductors of heat and electric current.) have low boiling points, so many are gases at room temp. Nonmetals that are solid at room temp seem to be brittle.

Metalloids Elements with properties that fall between metals and nonmetals. A metalloid’s ability to conduct electric current varies with temp.

Variation Across a Period Across a period from left to right, the elements become less metallic and more nonmetallic in their properties.

Valence Electrons Electrons in the outer most energy level of an atom. Within groups, atoms have the same amount of valence electrons. This gives them similar properties.

The Periodic Table Song https://www.youtube.com/watch?v=VgVQKCcfwnU

The Alkali Metals Group 1 on the periodic table. Single valence electrons Extremely reactive Reactivity increases from the top of the group to the bottom

The Alkaline Earth Metals Group 2 Have two valence electrons Harder than group 1 React differently with water

Boron Family Group 13 Three valence electrons Includes Al- the most abundant metal in Earth’s crust

Carbon Family Group 14 Four valence electrons Except for water, most of the compounds in your body contain carbon.

Nitrogen Family Group 15 Contains two nonmetals, two metalloids, and one metal Very different properties, but all have five valence electrons

Oxygen Family Group 16 Six valence electrons Three metals and two metalloids Oxygen is the most abundant element in Earth’s crust.

Halogens Group 17 Seven valence electrons Highly reactive nonmetals

Noble Gases Group 18 Helium has only 2 valence electrons The rest have 8 valence electrons Colorless, odorless, and extremely unreactive.