Nomenclature-+Chapters+7,+8,+9

Ellen Mahoney (editor) This wiki deals with nomenclature, including and Chapter 7: Ionic and Metallic Bonding, Chapter 8: Covalent Bonding, and Chapter 9: Chemical Names and Formulas. Chapter 7 talks about valence electrons, ionic compounds, and bonding in metals. Chapter 8 is about molecular compounds, the nature of covalent bonding, bonding theories, and polar bonds and molecules. Chapter 9 deals with naming ions, writing formulas, molecular compounds, acids and bases and laws. This is a short video explaining one part of nomenclature covered in these chapters: []
 * Nomenclature: Chapters 7, 8, and 9 **

** Group 1: Valence Electrons (Section 7-1) ** Kyle Mahoney (pg. 187-190)

**//Valence Electrons are the electrons in the highest occupied energy level of an element's atoms.//**
 * The number of valence electrons largely determines the chemical properties of an element.
 * To find the number of valence electrons in an atom of a Representative Element, simply look at it's group number on the periodic table.
 * Ex. Group 1A on the periodic table (Hydrogen, Lithium, Sodium, Potassium, and so forth,) all have one valence electron, corresponding to the group 1A.



= ** The Octet Rule ** = //**In forming compounds, atoms tend to achieve the electron configuration of a noble gas, meaning they try to obtain an octet, a set of eight electrons in their valence.**//
 * They try to become like noble gases, full on electrons so they won't react with anything anymore.
 * __Atoms of the metallic elements tend to lose their valence electrons, leaving a complete octet in the next-lowest energy level. Atoms of some nonmetallic elements tend to gain electrons or to share electrons with another nonmetallic element to achieve a complete octet.__
 * There are exceptions, but most compounds follow this rule.

=** Formation of Cations **=

// **An atom's loss of valence electrons produces a cation, or a positively charged ion.** //


 * Note: For metallic elements, the name of a cation is the same as the name of the element.
 * (ex. A Sodium cation, Na+, a Calcium cation, Ca2+)
 * Cations can be extremely different in terms of their chemical properties. For example, sodium is very explosive with water, but when it forms a cation in table salt, it is stable in water.


 * The most common cations are those formed by the loss of valence electrons from metal atoms, which are easily removed.
 * The cation will usually stop losing electrons when it loses all of them it had in it's valence shell, which follows the Octet Rule.


 * ** For transition metals, the charges of cations may vary. **
 * Ex. An atom of iron may lose two or three electrons.
 * It could lose two or three electrons, so you must write the cation appropriately to how many it lost, (Fe2+, Fe3+)


 * Some Transition metals will form ions that do not have a noble-gas configuration, which means they will not follow the Octet Rule.
 * = In this case, the atom will try to fill it's last orbital, and then be happy, silver only gets +1 because it only loses its 5s1 electron so that the other orbitals, (4s2 4p6 4p10 ) gets filled up. =

Hannah Mullen (pg. 191-193) = **Formation of Anions** =
 * Anions are atoms with a negative (-) charge
 * When atoms with no charge gain electrons, they become anions
 * Anion names often end in "ide" (if it is a nonmetallic element)
 * Note: In the picture below, "group 15" is Group 5A, "16" is 6A, etc.




 * Nonmetallic elements typically form anions because it is simpler for them to gain valance electrons to complete an octet (8 electrons in outer energy level) due to their nearly full outer energy level
 * For example: Bromine gains one valence electron to complete its outer energy level. This gives it a negative charge because electrons are negative. This makes Bromine Brˉ, or Bromide.
 * When Halogens (Group 7A) like Bromine gain electrons, they are called halide ions.
 * These ions are formed by the addition of only one electron. The formation of a halide ion is shown below:


 * Sulfur is in group 6A. This means it has 6 valence electrons. To complete the octet, it gains two electrons. This gives it a negative 2 charge. Sulfur then becomes Sulfide (S²ˉ).

**Group 2: Ionic Compounds (Section 7-2)** Lexie St. Jacques (pg. 194-200)

= Formation of Ionic Compounds =
 * ionic compounds- compounds composed of cations and anions
 * usually composed of metal cations and nonmetal anions
 * **Although they are composed of ions, ionic compounds are electrically neutral.**
 * Total positive charge of the cations = total negative charge of anions

**Ionic Bonds**
 * Anions and cations have opposite charges
 * attract one another by means of electrostatic forces
 * ionic bonds- the electrostatic forces that hold ions together in ionic compounds
 * ionic bonds are formed in chemical reactions

**Formula Units**
 * Chemists represent a substances' composition by using chemical formulas
 * Chemical formula- shows the kinds and numbers of atoms in the smallest representative unit of a substance
 * NaCl is the chemical formula for sodium chloride, however it does not represent a single discrete unit
 * an ionic compound exists as a collection of positively and negatively charged ions arranged in repeating patterns
 * because of this, its chemical formula refers to a ratio known as a formula unit
 * formula unit- the lowest whole-number ratio of ions in an ionic compound
 * ionic charges are used to derive the correct formula, but are not shown when you write the formula unit of the compound

= **Properties of Ionic Compounds** =
 * Most ionic compounds are crystalline solids at room temperatur e.
 * component ions in these crystals arranged in repeating three-dimensional patterns
 * **Ionic compounds generally have high melting points.**
 * coordination number- the number of ions of opposite charge that surround the ion in a crystal
 * internal crystal structures differ
 * **Ionic compounds can conduct an electrical current when melted or dissolved in water.**
 * when dissolved, ions are free to move

**Group 3: Bonding in Metals (Section 7-3)** Kyle St. Pierre (pg. 201-205)

**Metallic Bonds and Metallic Properties**

- Metals are made up of closely packed cations rather than neutral atoms

- Valence electrons are moving and can drift freely from metal to metal

- Metallic bonds consist of the attraction between the free-floating valence electrons for the positively charged metal ions

- Metals are good conductors of electrical currents because electrons can flow freely in them

- They are also malleable

- The reason for both of these is the mobility of the electrons

- The sea of valence electrons insulates the metal cations from one another



**Crystalline Structures of Metals**

- Metals are crystalline

- Metal atoms are arranged in very compact and orderly patterns

- There are many closely packed arrangements possible




 * Alloys **

- Alloys are mixtures composed of two or more elements, at least one of which is metal

- Their properties are often superior tot hose of heir component elements

- Nonferrous metals and aluminum alloys are used to create coins

- Steel is one of the most important alloys around at the current time

- It is useful because it has corrosion resistance, ductility hardness, and toughness

- It is often seen in buildings today because it offers a wider amount of possibilities in the structure

- A substitutional alloys are formed when the component atoms are about the same size and they replace each other in the crystal

- Interstitial alloys are formed when the atomic sizes are different, so the smaller atoms fit into the interstices between the larger atoms



**Group 4: Molecular Compounds (Section 8-1)** Marie Wachter (pg. 213-216)

**Molecules and Molecular Compounds**
 * Noble gas elements are monoatomic
 * exist in single atoms
 * **Covalent bond**: when an atom is held together by sharing electrons
 * like a "tug of war"
 * **Molecule**: a neutral group of atoms joined together by covalent bonds
 * **Diatomic molecule**: a molecule consisting of 2 atoms
 * Ex: oxygen molecule
 * Compounds are atoms bonded to each other to form molecules
 * [[image:mrdesjardinsdd12wiki/Picture_4.png]]
 * Compounds composed of molecules are **molecular compounds**
 * molecules of a given molecular compound are all the same
 * Ionic compounds exist as collections of positively and negatively charged ions arranged in repeating 3 dimensional patterns
 * **Molecular compounds tend to have relatively lower melting and boiling points than ionic compounds**
 * Most are gases or liquids at room temp.
 * most formed with 2 or more non-metals
 * most formed with 2 or more non-metals

**Molecular Formulas**
 * **Molecular formula**: a chemical formula of a molecular
 * **Show how many atoms of each element a molecule contains**
 * Water- 2 hydrogen 1 oxygen
 * H 2 O
 * subscript indicates number of atoms
 * not necessarily lowest whole - number ratios
 * subscript 1 is left out
 * Reflect the actual number of atoms in each molecule
 * Describe molecules consisting of one element
 * Oxygen molecule is 2 atoms bonded together
 * O 2
 * [[image:mrdesjardinsdd12wiki/bonding_types-oxygen.gif]]
 * Does not tell you about a molecule's structure

**Group 5: The Nature of Covalent Bonding (Section 8-2)** Jonathan Bailey (Pages 217-222)

**The Octet Rule in Covalent Bonding**


 * Electrons tend to be transferred so that each ion acquires a noble gas configuration.
 * In forming covalent bonds, electron sharing usually occurs so that atoms attain the electron configurations of noble gases.
 * Combinations of atoms in groups 4A, 5A, 6A and 7A on the periodic table are likely to form covalent bonds (non-metallic elements).
 * The “octet” comes from the maximum of 8 electrons that the atoms try to acquire when bonding.


 * Single Covalent Bonds **


 * Two atoms that are held together by sharing a SINGLE pair of electrons are joined by a **Single Covalent Bond.**
 * An electron dot structure such as **H:H** represents the shared pair of electrons between the two elements
 * **Structural Formula:**Represents the covalent bonds by dashes and the arrangement of covalently bonded atoms. (Such as H-H)
 * An example of a noble gas molecule that combines with itself to attain 8 electrons for both atoms is the Fluorine molecule.

A pair of valence electrons that is not shared between the atoms. (Also known as a lone pair or a nonbonding pair)
 * Unshared Electron Pairs: **


 * Water is a good example of three molecules that have unshared electron pairs, they use these to all attain noble gas configuration when they combine Hydrogen and Oxygen to make water.

You can draw the electron dot structure for atoms like these in similar ways, such as for an ammonia molecule.



Methane has 4 single covalent bonds in its electron dot structure, if 4 Hydrogen atoms were combined with one Carbon atom, it would form four identical single covalent bonds.



Note: When carbon forms bonds with other atoms, it usually makes four bonds!

**Double and Triple Covalent Bonds**


 * Atoms that share more than one pair of electrons can form double and triple covalent bonds.


 * __Double covalent bond:__** A bond that shares 2 pairs of electrons


 * __Triple Covalent Bond:__** A bond that shares 3 pairs of electrons

An example of how atoms form double covalent bonds are 2 Oxygen atoms bonding together, because they each have six valence electrons.



An example of how atoms form triple covalent bonds are 2 Nitrogen atoms bonding together, because they each have 5 Valence electrons, which means that they each need three to attain a noble gas configuration.



Nick Achin (pg. 223-229)

** Coordinate Covalent Bonds **

 * Coordinate covalent bonds are covalent bonds in which one atom contributes both bonding electrons.
 * This is shown by arrows pointing the electrons being shared.
 * Once they are formed they are the same as other covalent bonds.
 * A polyatomic ion is a tightly bound group of atoms that has a positive or negative charge and works as a unit.
 * Example: Ammonium Ion- NH 4+
 * Most polyatomic ions contain covalent and coordinate covalent bonds.
 * Have both ionic and covalent bonding.
 * The electron dot structure for a neutral molecule contains the same number of electrons as the total number of valence electrons in the combining atoms.
 * Since a negatively charged polyatomic ion is part of an ionic bond, the positive charge of the cation balances these electrons.

**Bond Dissociation Energies**
**Resonance**
 * The amount of energy required to break the bond between two covalently bonded atoms is the bond dissociation energy.
 * Expressed as the amount of energy to break one mole of bonds.
 * The stronger the bond, the higher the bond dissociation energy.
 * A resonance structure is a structure that occurs when it is possible to draw two or more valid electron dot structures that have the same number of electron pairs for a molecule or ion.
 * Double arrows are used to connect resonance structures.
 * Resonance structures can represent hybrid bonds.

**Exceptions to the Octet Rule**

 * The octet rule does not satisfy molecules with an odd number of valence electrons.
 * It also does not satisfy molecules with more or fewer valence electrons then a complete octet.
 * These molecules are still present, but cannot be drawn following octet rules.
 * Some atoms, including sulfur and phosphorus, that expand the octet to 10 or 12 electrons.

**Gr****oup 6: Bonding Theo** **ries (Section 8-3)**

Joe Jennings (pg. 230-233)

In Molecular Orbitals, atomic orbitals overlap in bonded atoms that apply to the whole atom. Orbitals that can be filled with two electrons from a colavent bond are called bonding orbitals. If 2 p-orbials combine to become symmetrical around the nucleus, it is a sigma orbital. If a P-orbital has 2 electrons, it becomes a pi bond. It has 2 regions of electron clouds. VSEPR Theory states that Electron Pairs repulse each other and cause molecules to adjust so the pairs are as far apart as possible. This is why molecules bend and are found in different shapes.

Darby Barrett (pg. 233-236)

In a water molecule, oxygen forms single covalent bonds with two hydrogen atoms: This makes water molecules have a bent shape

In contrast, carbon in a carbon dioxide molecule has no unshared electron pairs Therefore, carbon dioxide is a linear molecule

A bent water molecule (above) vs. a carbon dioxide molecule (below)



Possible molecular shapes are shown below



The VSEPR theory works well when accounting for molecular shapes, but it does no help much in describing the types of bonds formed- Orbital hybridization provides information about both molecular bonding and molecular shape Hybridization is when several atomic orbitals mix to form the same total number of equivalent hybrid orbitals

Videos to help you understand hybridization: [|First Hybridization Video] [|Secnd Hybridization Video] [|Quiz: Do You Understand How To Hybridize?] [|Did You Get It? Review/Quiz] There can be hybridization involving single, double, or triple bonds!

**Group 7: Polar Bonds** **and Molecules (Section 8-4)** __Sam__ Massoud (pg. 237-240)

**Bond Polarity**
Covalent bonds (bonds with a shared pair of electrons) are either **polar** or **nonpolar**.
 * ** Nonpolar covalent bonds ** occur when atoms in the bond pull equally and the bonding electrons are shared equally
 * Have the same charge




 * ** Polar covalent bonds ** occur when atoms in the bond are not shared equally
 * Have opposite charges




 * The higher the electronegativity value, the greater the ability of an atom to attract electrons to itself

**Polar Molecules** In a **polar molecule**, one end of the molecule is slightly positive and the other end is slightly negative

If a molecule has two poles, or regions with opposite charges, the molecule is **dipole**
 * The molecule in the diagram above is **dipole** because of its two oppositely charges poles

The polarity of a molecule depends on its shape
 * If the molecule is linear and all atoms lie on the same axis, the polarities cancel because they go in opposite directions




 * Water, however, has a bent shape. The polarities do not cancel and the molecule remains polar



Elena Berube (pg. 240-244)

**Attractions Between Molecules**
There are a variety of different forces that molecules can attract each other by, all of which can determine whether a molecular compound is a gas, liquid or solid at a given temperature.*

The different types of forces are....
 * Dipole Interactions: the attraction occurs between oppositely charged regions of polar molecules. The slightly negative region is attracted to the slightly positive region of another polar molecule. It is a type of ** Van der Waals force. **
 * This occurs for polar molecules as they have a permanent dipole moment. A molecule with a dipole has a "positive end" and a "negative end". When two or more such molecules come together they arrange themselves to maximum the attractive forces (negative near positive) and minimize the repulsive forces (like charges). Dipole forces can be strong and have a long range interactions.

This diagram shows the geometry of hydrogen and atoms in the water molecule, which is a dipole interaction .




 * Dispersion Forces: the weakest molecular interaction that occurs between nonpolar molecules when the moving electrons are on the side closest to the neighboring molecule. They have an electric force that influences the neighboring molecule’s electrons. This is also one of the **Van der Waals forces.**
 * Hydrogen bonds: forces in which a hydrogen is covalently bonded to an electronegative atoms that is also weakly bonded to an unshared electron pair that is also an electronegative atom.


 * Intermolecular Attractions and Molecular Properties **
 * The physical properties of a compound depend on the type of bonding that it displays, particularly whether it is covalent or ionic.
 * In most solids formed by molecules, only the weak attractions need to be broken.
 * o A **Network Solid** is a solid that has all covalent bonds. To melt a network solid, all of the covalent bonds throughout the solid would have to be broken.
 * o A Diamond is an example. It is a network solid form of carbon:



**Group 8: Naming Ions (Section 9-1)** Lauren Berube (pg. 253-255)

- Monatomic ions are made up of a single atom with a positive or negative charge resulting from a loss or gain of valence electrons
~ Cations that have a +1 charge are commonly found in Group 1A ~ Cations that have a +2 charge are commonly found in Group 2B ~Aluminum is the only Group 3A metal that will __form__ a +3 charge
 * Cations **

~ Nonmetals tend to __gain__ electrons to form anions ~ To name anions, start with the stem of the element's name and end with -ide ~ Group 7A has a charge of -1 ~ Group 6A has a charge of -2 ~ Group 5A has a charge of -3 ~The majority of elements in groups 4A and 8A do not form anions
 * Anions **

~ Transition metals can form more than 1 cation ~ The specific charge can only be determined by the number of electrons lost ~ There are many ways to name these cations
 * Ions of Transition Metals **

~ One way is the Stock System - in this system, roman numerals are placed in parenthesis to indicate the numerical value of charge ~ Another way is to use the root word and add suffixes onto the end

Brittany Chlebek (pg. 256-259)


 * Pharmacist: **
 * pharmacists have the responsibility to prepare the medicine, prescribed by the doctor, and to advise the patient about possible side effects
 * must check the doctor has not prescribed a medication that is too high in dosage or harmful to the patient
 * to become a pharmacist, you need a college degree in pharmacy
 * includes studies in chemistry, biology, mathematics, and statistics
 * must learn the biological effects of medication
 * Polyatomic Ions: **
 * polyatomic ions - composed of more than one atom
 * tightly bound groups of atoms that behave as a unit and carry a charge
 * the names of most polyatomic ions end in -ite or -ate or -ium or -ide
 * charge of each polyatomic ion in a given pair is the same
 * all anions containing the ending -ite or -ate contain oxygen

http://www.youtube.com/watch?v=TZgv21FmEzk

[|Explaining Polyatomic Ions]

**Group 9: Writing Formulas (Section 9-2)** Emily Crawford (pg. 260-263)

**Naming and Writing Formulas for Ionic Compounds**
__Binary Ionic Compounds__ o Binary compound- composed of two elements and can be either ionic or molecular o Knowing the compound’s formula means knowing the compound’s name o First compound must be composed on a monatomic metallic cation and a monatomic nonmetallic anion o Some transition metals have more than one ionic charge o Charges of monatomic anions are determined with the periodic table o Charges of polyatomic ions vary o If you know the name, you can write the formula. o Write the symbol of the cation and then the anion, and the balance the charges using subscripts. o The positive charge must balance the negative charge to equal zero. Ex) Calcium Bromide o The crisscross method also works to make formulas.
 * Before chemistry truly developed to what it is today, compounds were named using physical properties
 * Today, chemicals are named based on chemical composition
 * Antoine-Laurent Lavoisier helped create the systematic naming method which is still used today
 * Naming Binary Ionic Compounds
 * The name of the cation is placed first and is followed by the name of the anion
 * Writing Formulas for Binary Ionic Compounds
 * Calcium is Ca and has a charge of + 2
 * Bromine is Br and has a charge of – 1
 * Therefore +2 + -1= 1 and one atom of Ca does not balance one atom of Br.
 * An additional atom of Br is need to balance the equation.
 * The formula is CaBr2

o Make sure to reduce all ratios! Ex) Ca2S2 should really be CaS because 2:2 can be reduced to 1:1 media type="youtube" key="7Lfc6jjp1WQ" width="425" height="350" Melanie Brondyk (pg. 264-267)

Binary compounds do not contain more than two elements

 * Ex.) Calcium Carbonate (CaCO­3­)
 * “-Ate” or “-ite” ending on the name of a compound indicates that the compound contains a polyatomic anion that includes oxygen in the above example
 * How to write the formula for an ionic compound with a polyatomic ion:
 * Write the symbol for the cation followed by the formula for the polyatomic ion and balance the charges
 * Ex.) calcium nitrate is composed of calcium cation & and apolyatomic nitratie anion. Calcium nitrate has two nitrate anions (each with a -1 charge), which need to balance the 2+ charge of each calcium cation
 * The charge needs to be balanced
 * The ions are in the lowest whole number ratio
 * Use parentheses to set off the polyatomic ion in a formula only when the compound contains more than one polyatomic ion

**Naming Compounds with Polyatomic Ions **

 * ======Recognize that the compound contains a polyatomic ion; If not, look at Common Polyatomic Worksheet ======
 * ======To name a compound containing a polyatomic ion, state the cation first, and then the anion just as you did in naming binary ionic compounds ======
 * ======Some ionic compounds containing polyatomic ions do not include a metal cation ======
 * ======The cation may be the polyatomic ammonium ion ======

**Group 10: Molecular Compounds (Section 9-3)** Korey Dufault (pg. 268-270) **Naming Binary Molecular Compounds:**

**Binary ionic compounds are composed of the ions of two elements, a metal and a nonmetal.**

 * == **Binary molecular compounds are also composed of two elements, but both elements are nonmetals and they are not ions.** ==
 * == **Binary molecular compounds are composed of molecules, not ions, so ionic charges cannot be used to write formulas or to name them.** ==
 * == Prefixes in the names of binary molecular compounds help distinguish compounds containing different amounts of the same two elements. ==
 * == The prefix in the name of a binary molecular compound tells how many atoms of each atom are present in each molecule of the compound. ==

Table 9.4 lists the prefixes used to name binary molecular compounds.

 * == According to the table, the prefix //mono -// indicates the presence of one oxygen atom in CO. ==
 * == The prefix //di -// indicates the presence of the two oxygen atoms in CO2. ==
 * == The names of all binary compounds end in //- ide//. ==
 * == **Also note that the vowel at the end of a prefix often is dropped when the name of the element begins with a vowel.** ==
 * == **For CO, you would write carbon //mon//oxide, not carbon //mono//oxide.** ==
 * == If just one atom of the first element is in the formula, omit the prefix //mono -.// ==
 * == **Guidelines for naming binary molecular compounds:** ==
 * == First, confirm that the compound is a binary molecular compound -- that is, a compound composed of two nonmetals. ==
 * == The name must identify the elements in the molecule and indicate the number of each atom of each element. ==
 * == Use prefixes to indicate the number of each kind of atom. ==
 * == Omit the prefix //mono -// when the formula contains only one atom of the first element in the name. ==
 * == The suffix of the name of the second element is //- ide.// ==

media type="youtube" key="0oNAemORKdo" height="315" width="420"


 * == **This video will help you in naming Binary Molecular Compounds.** ==

**Writing Formulas for Binary Molecular Compounds:**
 * == Use the prefixes in the name to tell you the subscript of each element in the formula. Then write the correct symbols for the two elements with the appropriate subscripts. ==
 * == An example would be dinitrogen tetroxide. The prefix //di -// before nitrogen tells you that the compound contains two nitrogen atoms; the prefix //tetra -// tells you that the molecule also contains four oxygen atoms. Thus the formula for dinitrogen tetroxide is N2 O4. ==

media type="youtube" key="DFw3AW2BFUw" height="315" width="560"


 * == **This video will help you in writing formulas for Binary Molecular Compounds.** ==

**Group 11: Acids and Bases (Section 9-4)** Maddie Harmon (pg. 271-273) ~An acid is a compound that contaiins one or more hydrogen atoms ~When dissolved in water, acids produce hydrogen ions ~Generally, acids consist of an anion combined with many hydrogen ions necessary to make the molecule electrically neutral ~Chemical formulas of acids are normally written as HnX ~X is a monatomic or polyatomic anion ~n represents the number of hydrogen ions that combined with the anion ~There are three rules to follow to name an anion following the general formula of HnX 1. If the name of the anion ends in //-ide//, then the acid name begins with the prefix //hyrdo-.// The stem of the anion has the ending //-ic//, and is followed by the word acid. ~HCl would be hydrochloric acid 2. If the anion name ends in //-ite//, the acid name is the stem of the anion with the suffix //-ous//, followed by the word acid. ~H 2 SO 3 would be sulfurous acid 3. If the anion name ends it //-ate,// the name of the acid is the stem of the anion with the suffix //-ic// followed again by the word acid. ~HNO 3 would be nitric acid This game can help you review how to name each acid from a given formula
 * Naming Acids **

[]

**Writing Formulas for Acids** **~**Use the rules for naming the acids in reverse to write the formulas for acids ~For example: Hydrobromic acid is HBr, Phosphorous acid is H 3 PO 3, and Formic acid is HCOOH. ~Use this worksheet as a way to practice naming acids

[]

**Names and Formulas for Bases** **~**A base is an ionic compound that produces hydroxide ions when dissolved in water ~Bases are named in the same way that other ionic compounds are named ~The name of the cation is followed by the name of the anion. ~To write the formula for a base, write the symbol for the metal cation ~Then, write the formula for the hydroxide ion ~For example: aluminum hydroxide is the aluminum cation, Al 3+, and the hydroxide anion, OH -. ~Since you need 3 hydroxide ions to balance out the 3+ charge, the formula would be Al(OH) 3.

media type="youtube" key="CVgi74kswPA" height="187" width="336"

**Group 12: The Laws (Section 9-5)** Sean Lydon (pg. 274-278) **The Laws of Definite and Multiple Proportions**
 * The **law of defininite proportions** states that in any chemical compound, the masses of the elements are always in proportion. This is because elements combine in whole-number ratios.
 * For example, in water (H2O) there are two atoms of hydrogen to one atom of oxygen. The mass of two hydrogens is about 2 amu and the mass of one oxygen is about 16 amu. Therefore, the ratio of O:H in all water is 8 :1, whether it's a small cup or in an ocean. Here is a link to a video that explains this law and this problem in greater detail:media type="youtube" key="nvTB2cMbWU8" height="219" width="392"


 * Another example uses Magnesium sulfide. 100 grams of this element broken down to its elements would result in 43.13 g of Mg and 56.87 g of S. The Mg:S ratio can be reduced to .758:1. This mass ratio doesn't change no matter how the compound is made or how much you have of it.
 * Here is a link to another video explaining this law: []

media type="youtube" key="l-IPd_r7ytw" height="218" width="392"
 * The **law of multiple proportions** states that whenever the same 2 elements form 2 or more compounds, the different masses of 1 element that combine with the same mass of the other element are in the ratio of small whole numbers.
 * Here is a video that explains this law and uses a good example:


 * Here is a link to another video that explains this law: [|http://www.youtube.com/user/ChemAssistBeta#p/search/0/D6HbmG8nIrU]

** Skills: Naming Chemical Compounds **
 * The above chart will help you determine the name of a chemical compund. When the chart asks if A is in group 1, 2, 13, it is asking if A is in groups 1A, 2A, 3A, or 4A.

ib **Skills: Writing Chemical Formulas**
 * Here is a link to videos that help in naming compounds:
 * Naming Binary Ionic Compounds- []
 * Naming Compounds with Polyatomic Ions: 2 videos- []
 * and [|ht] [|tp://www.youtube.com/watch?v=pNn-4nLgqhQ&NR=1&feature=endscreen]
 * Remember the following guidelines when writing a chemical formula from a chemicla name
 * An -ide ending usually means it's a binary compound. Barium sulfide is BaS.
 * An -ite or -ate ending means the formula has a polyatomic ion that contains oxygen. Copper (II) sulfate is CuSO 4.
 * Prefixes in a name usually mean it's a molecular compound. Dinitrogen pentoxide is N 2 O 5.
 * A Roman numeral after a cation's name shows the cation's charge. Iron (III) is Fe 3+.

For good practice, pause each video when the name or chemical formula of the compound is given and try to get the chemical formula or name, then continue the video to check your answer.
 * Here are links to videos that will help in naming compounds and writing chemical formulas:
 * Ionic Formula Writing- []
 * Writing Formulas for Ionic Compounds- [|http://www.youtube.com/user/ChemAssistBeta?ob=video-mustangbase#p/search/2/YZKNI907dmE]
 * Naming and Writing Molecular Compounds- [] (When he says covalent compound, he means molecular compound)
 * Writing Formulas for Polyatomic Compounds 1- []
 * Writing Formulas for Polyatomic Compounds 2- []