Using Information From the Periodic Table

When Atoms Combine The goal of every atom is to become stable This can be achieved by creating bonds with other elements to completely fill outer electron shells Atoms that are unstable—that is, atoms in which the outer electron level is not full—will react readily with atoms that can fill their outer electron level.

Determining How Atoms Will React  All elements exhibit an electron configuration.  Those that have stable configurations are less likely to react. -How do you determine if the atom is stable or unstable?  This can be completed using an electron dot diagram.  The symbol represents the nucleus  The dots represent the number of valence electrons

Let’s Practice 1. Determine the group number of the element. 2. Write the element symbol 3. Place dots (valence e-) in a clockwise position until you have reached 8.. (octet rule) 4. Do not place more than one electron at a time. (exceptions are H and He)

Achieving Stability  Although the goal is to become stable; all atoms will not be based on their electron configuration.  Some elements achieve this by transferring/sharing electrons, thus creating chemical bonds.  2 Major Types of Chemical Bonds  Ionic Bonds  Covalent Bonds

What is an Ion? Remember: Atoms are electrically neutral because????  An atom that carries an electrical charge is called an ion  If the atom loses electrons, the atom becomes positively charged –it becomes a cation  If the atom gains electrons, the atom becomes negatively charged- it becomes an anion

Ion Formation  All of the elements in Group I have one electron in their outermost energy level.  All of these elements can lose that one valence electron.  These atoms become cations with a positive one charge.

How can electrons travel?  Recall:  As electrons move from one energy level to another they gain and lose energy.  Going up an energy level = energy gained  Going down an energy level= energy lost  Ionization energy is the amount of energy used or required to remove an electron.  Using the periodic table…..  This energy increases across the period  Decreases from the top to the bottom of a group

Ionic Bonds  metallic atoms tend to lose electrons- becoming cations  Nonmetallic atoms tend to gain electrons to become negatively charged ions which are called anions.  These oppositely charged cations and anions are attracted to one another because of their opposite charges.  A chemical bond that occurs when  Electrons are transferred  Between cations and anions  Metals and nonmetals  High melting and boiling points  Conduct electricity when melted or dissolved in water  Many are soluble in water but not in non-polar liquid  Creates salts  Ex: Sodium( Na) and Chlorine (Cl) create NaCl (table salt)

Positive Ion (Cation) Formation Negative Ion (Anion) Formation Na has one valence electron. It loses it to Chlorine. Na now has a filled valence shell. (an octet) Becomes positive one in charge Chlorine has seven valence electrons. It gains one electron from Na. Chlorine now has filled octet. Chlorine has a negative one charge. (Chloride ion) Na +1 attracts Cl -1 and forms the ionic bond.

Covalent Bonds  involve the sharing of a pair of valence electrons by two atoms  Occurs between nonmetals  Can be polar(unequal pairing) or nonpolar(equal pairing)  Low melting points  Can be solid, liquid, or gas at room temperature.  Do not conduct electricity; non electrolytes

Naming Chemical Compounds and Balancing Equations

Chemical Reactions  A chemical reaction changes one set of chemicals into another set of chemicals.  Elements or compounds that enter into a chemical reaction are known as reactants. CO 2 + H 2 O  H 2 CO 3 (Reactants)

Chemical Reaction  The elements or compounds produced by a chemical reaction are known as products. CO 2 + H 2 O  H 2 CO 3 (Product)

All chemical reactions can be placed into one of five categories. Here they are, in no particular order:

 1) Combustion: A combustion reaction is when oxygen combines with another compound to form water and carbon dioxide. These reactions are exothermic, meaning they produce heat. An example of this kind of reaction is the burning of napthalene:  C 10 H O 2 ---> 10 CO H 2 O

 2) Synthesis: A synthesis reaction is when two or more simple compounds combine to form a more complicated one. These reactions come in the general form of:  A + B ---> AB  One example of a synthesis reaction is the combination of iron and sulfur to form iron (II) sulfide:  8 Fe + S 8 ---> 8 FeS

 3) Decomposition: A decomposition reaction is the opposite of a synthesis reaction - a complex molecule breaks down to make simpler ones. These reactions come in the general form:  AB ---> A + B  One example of a decomposition reaction is the electrolysis of water to make oxygen and hydrogen gas:  2 H 2 O ---> 2 H 2 + O 2

 4) Single displacement: This is when one element trades places with another element in a compound. These reactions come in the general form of:  A + BC ---> AC + B  One example of a single displacement reaction is when magnesium replaces hydrogen in water to make magnesium hydroxide and hydrogen gas:  Mg + 2 H 2 O ---> Mg(OH) 2 + H 2

 5) Double displacement: This is when the anions and cations of two different molecules switch places, forming two entirely different compounds. These reactions are in the general form:  AB + CD ---> AD + CB  One example of a double displacement reaction is the reaction of lead (II) nitrate with potassium iodide to form lead (II) iodide and potassium nitrate:  Pb(NO 3 ) KI ---> PbI KNO 3

 Follow this series of questions. When you can answer "yes" to a question, then stop!  1) Does your reaction have oxygen as one of it's reactants and carbon dioxide and water as products? If yes, then it's a combustion reaction  2) Does your reaction have two (or more) chemicals combining to form one chemical? If yes, then it's a synthesis reaction  3) Does your reaction have one large molecule falling apart to make several small ones? If yes, then it's a decomposition reaction  4) Does your reaction have any molecules that contain only one element? If yes, then it's a single displacement reaction  5) Does your reaction have water as one of the products? If yes, then it's an acid-base reaction  6) If you haven't answered "yes" to any of the questions above, then you've got a double displacement reaction

Try These Now! 24

Naming Ionic Compounds with Two Elements To name a compound that contains two elements, identify the cation and anion. name the cation first followed by the name of the anion. 25

Charges of Representative Elements 26 Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

Names of Some Common Ions 27 Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

Learning Check Complete the names of the following ions. Ba 2+ Al 3+ K + _________ __________ _________ N 3  O 2  F  _________ __________ _________ P 3  S 2  Cl  _________ __________ _________ 28

Solution Ba 2+ Al 3+ K + barium aluminum potassium N 3  O 2  F  nitride oxide fluoride P 3  S 2  Cl  phosphide sulfide chloride 29

Examples of Ionic Compounds with Two Elements Formula IonsName cation anion NaClNa + Cl - sodium chloride K 2 SK + S 2- potassium sulfide MgOMg 2+ O 2- magnesium oxide CaI 2 Ca 2+ I - calcium iodide Al 2 O 3 Al 3+ O 2- aluminum oxide 30

Learning Check Write the names of the following compounds. 1) CaO___________ 2) KBr___________ 3) Al 2 O 3 ___________ 4) MgCl 2 ___________ 31

Learning Check Write the formulas and names for compounds of the following ions: Br − S 2− N 3− Na + Al 3+ 32

Solution Br − S 2− N 3− Na + Al 3+ NaBr sodium bromide Na 2 S sodium sulfide Na 3 N sodium nitride AlBr 3 aluminum bromide Al 2 S 3 aluminum sulfide AlN aluminum nitride 33