Chapter 5. The Periodic Table

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Wesley Hensley
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1 Chapter 5 The Periodic Table

2 Periodic Table Russian, Dmitri Mendeleev, published the first periodic table. He arranged the elements into rows in order of increasing mass so that elements with similar properties were in the same column. Today the periodic table is arranged according to increasing atomic numbers. In a column, the masses increased from top to bottom. He left spaces between elements in the Periodic Table for missing elements that had yet to be discovered. Periodic Table is an arrangement of elements in columns, based on a set of properties that repeat from row to row. Because the properties of the elements repeat at regular intervals from row to row, it helps us to understand why the table of elements is called a Periodic Table.

4 ! 6 C 2 4 Carbon Tells you how many electrons and how many energy levels EX: 6 electrons- 2 in the first energy level and 4 in the second energy level. The top number is the atomic number. Every element has its own unique atomic number. The atomic number tells how many protons are in one atom of that element. Since no two elements have the same atomic number, no two elements have the same number of protons. Moving from left to right across a row the atomic number increases by exactly one from element to element. The large letter is the element's symbol, and just below that is the element's name. Each element has its own unique symbol and name. Below the name is the element's atomic mass. The atomic mass is the mass in atomic mass units for all possible isotopes of that element. It is a value that depends on the distribution of an element s isotopes in nature and the masses of those isotopes. The atomic mass of an element is the weighted average of all its isotope s masses. The unit for atomic mass is (amu) atomic mass unit.

5 Sec 2 The Periodic Table In the periodic table the elements are arranged by increasing atomic number. An element s properties can be predicted from its location in the periodic table. Each row in the Periodic Table is a PERIOD. The number of elements per period varies because the number of available orbitals increases from energy level to energy level. There are 7 Periods (horizontal rows). Each row contains different types of elements from different groups and they have different properties. The period number an element is in tells you how many energy levels (which contains electrons) it has. ( All elements in Period 3 have 3 energy levels. ) Across a period from left to right, the elements become less metallic and more nonmetallic in their properties.

6 Each column on the periodic table is called a GROUP. There are 18 Groups or Families. The elements in a group have similar characteristics and properties, but not identical characteristics. The elements in a group also have similar electron configuration. This pattern of repeating properties of elements shown in the P.T. is known as the Periodic Law.

7 Valence Electrons 1. Electrons farthest away from the nucleus. The electrons in the highest occupied energy level of an atom of that element. 2. They play a key role in chemical reactions. They are used to form chemical bonds (the force which bond atoms together). So the tendency of an element to react is closely related to the number of valence electrons in the atoms of an element. 3. The valence electrons increase from left to right in a period. 4. Elements in the same group have similar properties because they have the same number of valence electrons. This explains why Hydrogen is placed with metals. Hydrogen has 1 valence electron in its outer energy level just like Lithium, Sodium and the other elements in Group 1.

8 Classes of Elements The periodic table presents three different ways to classify elements. 1. Elements are classified as solids, liquids, or gases, based on their states of matter at room temperature. The actual symbols are colored coded. Solids are black, liquids are in blue-purple and the symbols for gases are red. 2. Elements are divided into those that occur naturally and those that do not. All but 2 elements with atomic numbers 1-92 occur on Earth. Elements with atomic numbers 93 and higher do not occur naturally. The symbol for those elements are white. 3. Elements are classified as metals, nonmetals, and metalloids based on their properties.

9 METALS Most elements on the Periodic Table are classified as Metals. Metals are good conductors of electric current and heat Most metals are solids at room temperature except for mercury Most metals are malleable, they are not brittle. Many are ductile ( they can be drawn into thin wire) Some metals are extremely reactive ( like Magnesium) and some metals do not react easily ( like gold)

10 Nonmetals / Metalloids Nonmetals are elements that are poor conductors of heat and electric current. Many nonmetals are gases at room temperature. Nonmetals that are solids at room temperature tend to be brittle. Some are very reactive, some are not. Fluorine is the most reactive nonmetal. Metalloids- have both metal and nonmetal characteristics. A metalloid's ability to conduct electric current varies with temperature. Silicon (Si) and Germanium (Ge) are good insulators at low temperatures and good conductors at high temperatures.

Sec 3 Families or Groups Alkali- metals in Group 1 These metals are the most reactive metals. These elements have 1 valence electron that is easily transferred in a chemical reaction.

11 Sec 3 Families or Groups Alkali- metals in Group 1 These metals are the most reactive metals. These elements have 1 valence electron that is easily transferred in a chemical reaction. Because they are so reactive, alkali metals are found in nature only in compounds. EX: Na is found as the compound NaCl (salt), a compound of sodium and chloride. The reactivity (the tendency to react with other substances) of alkali metals increases from the top of Group 1 to the bottom within the group.

12 Alkaline earth metals Group 2! They all have 2 valence electrons. Most common are Mg (magnesium) used in frames of bicycles, and also plays a key role in the process that uses sunlight to produce sugar in plants-at the center of chlorophyll is magnesium. Ca (calcium) found in bones and teeth, and chalk, coral and limestone. Differences in reactivity among the alkaline earth metals are shown by the ways they react with water. Electron shells is same as Energy levels

13 Transition Metals Groups 3-12 The 38 elements in groups 3 through 12 of the periodic table are called "transition metals". As with all metals, the transition elements are both ductile and malleable, and conduct electricity and heat. They form a bridge between the very reactive metals on the left and the less reactive metals on the right side of the periodic table. The interesting thing about transition metals is that the electrons (valence electrons) they use to combine with other elements, are present in more than one energy level. One property of transition metals is their ability to form compounds with distinctive colors.. There are three noteworthy elements in the transition metals family--- iron, cobalt, and nickel, and they are the only elements known to produce a magnetic field.

14 Transition Metals Groups 3-12

15 The Boron Family lies in the 13 th Group. All these elements have 3 valence electrons. Aluminum is the most abundant metal in Earth s!!! crust. It is often found combined with oxygen in a mineral called Bauxite. Glass that contains boron is used to make laboratory glassware. The Carbon Family is Group 14. The elements in this group have 4 valence electron. Life on earth would not exist without carbon. Except for water, most of the compounds in your body contain carbon. Silicon is the second most abundant element in Earth s crust. It is found as silicon dioxide in quartz rock, sand, and glass. The metallic nature of these elements increase from top to bottom within the group.

16 The Nitrogen Family lies in Group 15. Each have 5 valence electrons in their outer energy level. Nitrogen is contained in fertilizers as well as phosphorus. The Oxygen Family is Group 16. All the elements in this group have 6 valence electrons. Oxygen is the most abundant element in Earth s crust. Sulfur was one of the first elements to be discovered because it is found in large natural deposits. It is used to make sulfuric acid, a compound in fertilizers.

The Halogens are the elements in Group 17. They have 7 valence electrons. Despite their physical differences, the halogens have similar chemical properties.

17 The Halogens are the elements in Group 17. They have 7 valence electrons. Despite their physical differences, the halogens have similar chemical properties. They are the most reactive nonmetals in the periodic table. They were given the name halogen from the Greek roots hal- ( salt ) and gen ( to produce or form ), because they all produce sodium salts of similar properties. Halogens react most easily with most metals. Fluorine is used to prevent tooth decay and Chlorine in used to kill bacteria in water and swimming pools.

18 The Noble Gases are the elements in Group 18. Helium has 2 valence electrons but the other Noble Gases have eight valence electrons. The Noble Gases are colorless and odorless and extremely unreactive. All the Noble Gases except Radon are used in neon lights like those in advertising signs.

19 Hyperlink to Periodic Table

Untitled Document. 1. Which of the following best describes an atom? 4. Which statement best describes the density of an atom s nucleus?

Untitled Document. 1. Which of the following best describes an atom? 4. Which statement best describes the density of an atom s nucleus? Name: Date: 1. Which of the following best describes an atom? A. protons and electrons grouped together in a random pattern B. protons and electrons grouped together in an alternating pattern C. a core