Periodic Table

He organized them by their increasing atomic masses. Dmitri Mendeleev organized the known elements into a table called the periodic table. He organized them by their increasing atomic masses.

Today we organize the elements by their increasing Atomic Number.

Insert copy of the periodic table.

Rows on the periodic table are called periods Rows on the periodic table are called periods. All the elements listed in a row belong to the same period. There are 7 (seven) periods.

Columns in the periodic table are called groups or families Columns in the periodic table are called groups or families. All elements in a group have similar properties.

Insert copy of the periodic table. The columns have been given an Arabic number. The columns are numbered 1 – 18 starting at the left and moving to the right. Please make sure that your periodic table has them numbered like this.

The outer most energy level is usually not full or complete . Valence Electrons The outer most energy level is usually not full or complete . These electrons in the outer energy level are called Valence electrons. Valence electrons are important because they determine how an element will react with other substance.

Insert picture of periodic table. Group 1 and 2 the number of Valence electrons in the outer energy level will match the group number.

Insert picture of periodic table. Groups 3 through 12 do not follow any particular rule to determine the number of Valence electrons.

Insert picture of periodic table. Group 13 to 18 – The Valence electrons for each of these is the group number less 10. For example Group 14 – 10 = 4 Valence electrons.

Elements whose atoms gain, lose or share electrons are reactive and they combine to form the many compounds we use in our daily lives.

Elements are categorized as metals, nonmetals or metalloids. Metals: An element that has luster, is malleable and ductile, and is said to be a good conductor of heat and electricity.

What is luster, malleable and ductile? Luster describes the way a surface reflects light…therefore metallic luster would be shiny like a metal object. Malleable means to be able to press or pound the substance into sheets or different shapes. Ductile means that the substance can be drawn out into thin wires.

Elements are categorized as metals, nonmetals or metalloids (cont’). Nonmetals: an element that is usually a gas or a brittle solid at room temperature. It is a poor conductor of heat and electricity.

Elements are categorized as metals, nonmetals or metalloids (cont’). Metalloid: an element that shares some characteristics or properties with both metals and nonmetals.

Group 1 and 2 Elements: These elements are so reactive that they are only found combined with other elements in nature.

Low Density (some will even float) Group 1: Alkali Metals Soft – can be cut with a knife Shiny and silver colored Low Density (some will even float) Most reactive of the metals Valence electrons = 1 Reacts violently with water forming a hydrogen gas Compounds from these are very useful such as NaCl 3 Li Lithium 6.941 11 Na Sodium 22.990 19 K Potassium 39.098 37 Rb Rubidium 85.468 55 Cs Cesium 132.905 87 Fr Francium 223.020

Silver colored Group 2: Alkaline- Earth Metals 4 Be Beryllium 9.012 12 Mg Magnesium 24.305 20 Ca Calcium 40.078 38 Sr Strontium 87.62 56 Ba barium 137.327 88 Ra Radium 226 Group 2: Alkaline- Earth Metals Very reactive but not as reactive as Alkali Metals. Silver colored More dense than Group 1 metals Valence electrons = 2 Useful compounds include: Calcium compounds such as cement, plaster, chalk, and YOU.

Higher density and melting points (except mercury) than Group 1 and 2 Group 3 to 12: Transition Metals Do not lose their valence electrons as easily as groups 1 & 2. Less reactive than Alkali and Alkaline Earth metals Shiny Good conductors of electricity Higher density and melting points (except mercury) than Group 1 and 2

Group 3 to 12: Transition Metals (cont’.) Lanthanides: The first row underneath the periodic table: Shiny, reactive, many are used in the production of steel. Actinides: The second row underneath the periodic table: These elements are all radioactive and unstable.. Note: Elements found after 94 (Plutonium) are man made and not found in nature

Poor Conductors of electricity and heat Group 17: Halogen Group Very reactive Valence electrons = 7 Nonmetal group Poor Conductors of electricity and heat React violently with alkali metals to form salts Never found uncombined in nature Atoms of these elements only need to gain 1 electron to fill their outer shell Chlorine and Iodine are both in this group and can be combined to make disinfectants. 9 F Fluorine 18.998 17 Cl Chlorine 35.453 35 Br Bromine 79.904 53 I Iodine 126.904 85 At Astatine 210

Group 18: Noble Gases Valence electrons = 8 (He = 2) Outermost energy shell is full (complete) Under normal conditions they do not react with other elements

Most abundant element in the Universe 1 H Hydrogen 1.008 Hydrogen Stands Alone: Properties do not match the properties of any single group. Valence = 1 Most abundant element in the Universe .

Insert picture of periodic table.