-Describe how elements are arranged in the periodic table Arranging elements Objectives: -Describe how elements are arranged in the periodic table -Compare metals, non-metals and metalloids based on their properties and their location in the periodic table.

Organizing the elements according to their properties would help scientists understand how elements interact with each other.

Mendeleev’s Periodic Table In 1869, a Russian chemist and teacher published a table of the elements. Mendeleev arranged the elements in the periodic table in order of increasing atomic mass.

The Periodic Law In the modern periodic table elements are arranged in order of increasing atomic number. Periodic Law states: When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

The periodic table is made up of rows of elements and columns. An element is identified by its chemical symbol. The number above the symbol is the atomic number The number below the symbol is the rounded atomic mass of the element. A row is called a period A column is called a group

The elements can be grouped into three broad classes based on their general properties. Three classes of elements are Metals, Nonmetals, and Metalloids.

Properties of Metals Metals are good conductors of heat and electricity. Metals are shiny. Metals are ductile (can be stretched into thin wires). Metals are malleable (can be pounded into thin sheets). A chemical property of metal is its reaction with water which results in corrosion. Solid at room temperature except Hg.

Properties of Non-Metals Non-metals are poor conductors of heat and electricity. Non-metals are not ductile or malleable. Solid non-metals are brittle and break easily. They are dull. Many non-metals are gases. Sulfur

Properties of Metalloids Metalloids (metal-like) have properties of both metals and non-metals. They are solids that can be shiny or dull. They conduct heat and electricity better than non-metals but not as well as metals (Semiconductors) They are ductile and malleable. Silicon

Grouping the Elements Objectives Describe the difference between period and group. Explain why elements in a group often have similar properties. Describe the properties of elements and the groups of the periodic table.

The properties of the elements in a group are similar because the atoms of the element have the same number of electrons in their outer energy level. What are energy levels?

Energy level refers to how the electrons are configured in an atom or molecule.

Atoms will often take, give, or share electrons in their outer energy level. Elements whose undergo such processes are called reactive and can form compounds.

Hydrogen The hydrogen square sits atop group 1, but it is not a member of that group. Hydrogen is in a class of its own. It’s a gas at room temperature. It has one proton and one electron in its one and only energy level. Explosive reactions with oxygen Used as fuel in rockets

Four chemical groups of the periodic table: alkali metals (1) alkaline earth metals (2) Transition Metals (3-12) Boron group (13) Carbon group (14) Nitrogen group (15) Oxygen group (16) Halogens (17) Noble gases (18)

Alkali Metals The alkali family is found in the first column of the periodic table. Atoms of the alkali metals have a single electron in their outermost level, in other words, 1 valence electron. They are shiny, have the consistency of clay, and are easily cut with a knife.

Alkali Metals They are the most reactive metals because their atoms can easily give away the one outer-level electron They react violently with water and form hydrogen gas. Alkali metals are never found as free elements in nature. They are always bonded with another element.

Alkaline Earth Metals They have two valence electrons. Alkaline earth metals include magnesium and calcium Magnesium can be mixed with other metals to make low-density materials used in airplanes.

Transition Metals Transition Elements include those elements in the groups 3-12 These are the metals you are probably most familiar with: copper, tin, zinc, iron, nickel, gold, and silver. They are like metals, shiny and good conductors of heat and electricity.

Transition Elements Open page 346

Boron Group Have 3 valence electrons Reactive Solids at room temperature Most common element is Aluminum

Carbon Group Have 4 valence electrons Solids at room temperature Reactivity varies among elements Carbon is essential for living organisms since it forms a wide range of compounds such as fats, proteins and carbohydrates.

Nitrogen Group Have 5 valence electrons Reactivity varies among elements Solids at room temperature except for Nitrogen. Nitrogen makes up 80% of the air you breathe.

Oxygen Group Have 6 valence electrons. Reactive Solids at room temperature except for oxygen Oxygen is crucial for all living organisms. Sulfur is used to make sulfuric acid, the most common compound in the chemical industry.

Halogens Nonmetals Have 7 valence electrons Very reactive since they need just one electron to have a complete outer level. Usually react with metals to gain the missing electron. The reaction of halogen with metal makes a salt. Chlorine and iodine are used as disinfectants.

Noble gases Nonmetals complete outer energy level, 2 valence electrons in Helium and 8 in the rest Un-reactive Colorless, odorless gases at room temperature Neon is used to make “neon” lights

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