# Chemical Bonding and Nomenclature Chemical Bonding and Nomenclature.

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Chemical Bonding and Nomenclature Chemical Bonding and Nomenclature

s 8 I want you to meet a friend of mine? Bonding, the way atoms are attracted to each other to form molecules, determines nearly all of the chemical properties we see. And, as we shall see, the number “8” is very important to chemical bonding.

5.1 What are Molecules? Molecules are a combination of atoms bonded together. Bonding determines the chemical properties of the molecule (compound).

VALENCE ELECTRONS The number of valence electrons determines the chemical properties of an element The number of valence electrons determines the chemical properties of an element Electrons that engage in bonding to form molecules and compounds Electrons that engage in bonding to form molecules and compounds

Groups - Review Each column is called a “group” Each element in a group has the same number of electrons in their outer orbital, also known as “shells”. Except for He, it has 2 electrons The electrons in the outer shell are called “valence electrons” www.chem4kids.com

VALENCE ELECTRONS B = 1S 2 2S 2 2P 1

Octet rule Group 8 – noble gases Group 8 – noble gases Have 8 valence electrons Have 8 valence electrons Stable and unreactive in chemical reactions Stable and unreactive in chemical reactions Atoms will react with each other in order to attain 8 valence electrons ( octet=8) Atoms will react with each other in order to attain 8 valence electrons ( octet=8) Gain or lose electrons – ions Gain or lose electrons – ions Share electrons Share electrons

Lewis Structures – visually show valence electrons 1) Find your element on the periodic table. 2) Determine the number of valence electrons. 3) This is how many electrons you will draw.

Lewis Structures 1) Write the element symbol. 2) Carbon is in the 4 th group, so it has 4 valence electrons. 3) Starting at the right, draw 4 electrons, or dots, counter- clockwise around the element symbol.

IONIC BONDING FORMING CATIONS AND ANIONS Atoms are electrically neutral due to equal numbers of electrons and protons Ions which are charged particles form when atoms or groups of atoms gain or lose electrons to form compounds Want to have an octet or be like the noble gases Oxidation numbers are assigned to keep track of electrons that are lost or gained

IONIC BONDING FORMING CATIONS AND ANIONS ANION = O becomes O -2 is an oxygen ion Oxidation number is -2 O will gain 2, (valence = 6) has more electrons that protons = negative overall CATION = Na becomes Na + - Na ion Oxidation number is +1 Na will give up 1, will never gain 7 Has more protons than electrons = positive overall The positive and negative ions are attracted to each other electrostatically.

Opposites Attract!

Formation of Ionic Compounds Formula Units Formula Units A chemical formula shows the kinds and numbers of atoms in the smallest representative unit of a substance. A chemical formula shows the kinds and numbers of atoms in the smallest representative unit of a substance. EX. NaCl, MgCl 2 EX. NaCl, MgCl 2 A formula unit is the lowest whole-number ratio of ions in an ionic compound. A formula unit is the lowest whole-number ratio of ions in an ionic compound. NaCl ( 1:1), MgCl 2 (1:2) NaCl ( 1:1), MgCl 2 (1:2) 7.2

Conceptual Problem 7.2

REVIEW QUIZ How many valence electrons are in How many valence electrons are in K ( potassium)Mg (magnesium) K ( potassium)Mg (magnesium) Draw the lewis dot structure for the above Draw the lewis dot structure for the above 3 points each 1 = formula 1 = correct symbol 1= lewis dot and correct depiction of bonding Al + Br

Review Na + and O 2- ? Na + and O 2- ? Write chemical formula? Write chemical formula? Name the compound Name the compound

NAMING IONS Compounds have a positive metal ion and a negative nonmetal ion combined together to form a neutral compound Compounds have a positive metal ion and a negative nonmetal ion combined together to form a neutral compound Monatomic ions = single atom with a positive or negative charge resulting from a loss or gain of valence electrons Monatomic ions = single atom with a positive or negative charge resulting from a loss or gain of valence electrons

NAMING CATIONS The names of cations are the same as the metal followed by the word ion or cation The names of cations are the same as the metal followed by the word ion or cation Ex. Na + = sodium cation (ion) Ex. Na + = sodium cation (ion) Al 3+ = aluminum cation (ion) Al 3+ = aluminum cation (ion)

NAMING ANIONS Nonmetals gain electrons forming anions Nonmetals gain electrons forming anions Naming Naming Start with the stem of the element name Start with the stem of the element name Add –ide Add –ide Ex. Chlorine = Chloride ion Ex. Chlorine = Chloride ion Sulfur = Sulfide ion Sulfur = Sulfide ion

Diatomic Compounds Use the full name of the cation (metal) written first Use the full name of the cation (metal) written first The anion (nonmetal) comes last and change ending to –ide The anion (nonmetal) comes last and change ending to –ide Sodium ChloridePotassium Nitride Sodium ChloridePotassium Nitride

TRANSITION METAL IONS Can form more than 1 cation Can form more than 1 cation Ex. Fe can lose 2 e- or it can lose 3 e- Ex. Fe can lose 2 e- or it can lose 3 e- These metals are designated by a roman numeral in parenthesis Fe (II) ion These metals are designated by a roman numeral in parenthesis Fe (II) ion If the metal has only one ionic charge you would not use a (I). If the metal has only one ionic charge you would not use a (I).

Writing Formulas From Names Identify the charge of the cation Identify the charge of the cation Identify the charge of the anion Identify the charge of the anion Criss Cross oxidation numbers to become the subscripts in the formula Criss Cross oxidation numbers to become the subscripts in the formula Aluminum SulfideAl 3+ S 2- Aluminum SulfideAl 3+ S 2- Al 2 S 3 Al 2 S 3

POLYATOMIC IONS Group of atoms that stay together and have a charge. Group of atoms that stay together and have a charge. ex. Sulfate anion = SO 4 2- Different endings depending on the number of o (oxygen) in the atom ex. NO 2 – = nitrite NO 3 - = nitrate

POLYATOMIC IONS Create a notecard the lists the names of polyatomic ions Create a notecard the lists the names of polyatomic ions This may be used on tests-if you forget it, you are out of luck !!! This may be used on tests-if you forget it, you are out of luck !!! Page 257 table 9.3 Page 257 table 9.3

Review Quiz Using correct oxidation numbers write the chemical formula of the following Using correct oxidation numbers write the chemical formula of the following Aluminum Oxide Aluminum Oxide Zinc Nitrate Zinc Nitrate Correctly name the following compounds Correctly name the following compounds Cu 3 P Cu 3 P Mn 2 (SO 3 ) 3 Mn 2 (SO 3 ) 3

PROPERTIES OF IONIC COMPOUNDS Most are crystalline solids at room temperature Most are crystalline solids at room temperature Arranged in repeating 3-D patterns Arranged in repeating 3-D patterns

MELTING POINTS Generally very high melting points Generally very high melting points Due to very large attractive forces between ions and crystal formation Due to very large attractive forces between ions and crystal formation

CONDUCTIVITY Ionic compounds can conduct an electric current when dissolved in water Ionic compounds can conduct an electric current when dissolved in water

Review Quiz Write the following formulas Write the following formulas Magnesium oxide Magnesium oxide Sodium sulfide Sodium sulfide Tin (II) flouride Tin (II) flouride Name the following compounds Name the following compounds MnO 2 MnO 2 CuCl 2 CuCl 2 Li 3 N Li 3 N

METALLIC BONDS/PROPERTIES Occur between two metals Occur between two metals Good conductors because electrons can flow freely Good conductors because electrons can flow freely Crystalline structure Crystalline structure Metals are arranged in a very compact and orderly fashion Metals are arranged in a very compact and orderly fashion

ALLOYS Most metals are alloys - mixture of two or more elements with at least one being a metal Most metals are alloys - mixture of two or more elements with at least one being a metal Ex. Brass, sterling silver, stainless steel, cast iron Ex. Brass, sterling silver, stainless steel, cast iron Usually more durable, harder ect.. Usually more durable, harder ect..

Review Problems Do 7.3 section assessment Do 7.3 section assessment