 Key Question: Why Do Atoms Combine In Certain Ratios?

Review of Oxidation Numbers

 All compounds have an electrical charge of zero (they are neutral).  An oxidation number indicates the charge on the atom (or ion) when electrons are lost, gained, or shared in chemical bonds.

Oxidation Numbers  A sodium atom always ionizes to become Na + (a charge of +1) when it combines with other atoms to make a compound.  Therefore, we say that sodium has an oxidation number of 1 +. What is chlorine’s oxidation number?

H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar The Number Of Electrons In The Outside Shell. The Number Of Electrons In The Outside Shell.

Ionic Bonds  On the periodic table, strong electron donors are on the left side (alkali metals).  Strong electron acceptors are on the right side (halogens).  The further apart two elements are on the periodic table, the more likely they are to form … an ionic compound.

Covalent Bonds  Covalent compounds form when elements have roughly an equal tendency to accept electrons.  Elements that are both nonmetals and therefore close together on the periodic table tend to form covalent compounds.

Oxidation Numbers, Lewis Structures And Chemical Formulas  Remember, the oxidation numbers for all the atoms in a compound must add up to zero.

Chemical Compound Quiz Sodium chloride is a flavorful addition to many foods. What is the common name? Salt

Multiple Oxidation Numbers  Some periodic tables list multiple oxidation numbers for most elements.  This is because more complex bonding is possible.

Euphemisms in Science We all know that some politicians and government spokesmen use certain euphemistic phrases to give an aura of respectability to descriptions of events or actions which would be offensive when expressed in plain English. The following is a list of Euphemisms in Science and their translations into plain English. “It has long been known...” I haven't bothered to look up any references!

Naming Compounds and Writing Formulas

3 Types Of Chemical Compounds Binary ionic - metal ion – nonmetal ion Ternary ionic - at least one ion is a polyatomic ion Binary molecular - two nonmetals

Tips To Keep In Mind When Naming And Writing Formulas: Always keep your Periodic Table handy – You should have it in front of you ALWAYS when you are naming and writing formulas. metalsRemember that metals (except Hydrogen) are found to the left of the stairstep on the Periodic Table. NonmetalsNonmetals are found on the right side of the stairstep on the Periodic Table.

Naming Binary Compounds  A binary ionic compound is held together by ionic bonds.  Binary molecular compounds consist of covalently bonded atoms.  Each type of compound has its own naming rules.

How Do You Name Binary Ionic Compounds? (Composed Of Two Elements – A Metal And A Nonmetal) Name the first ion (If the first ion is a transition element or tin or lead, you must use a Roman Numeral with the name – we’ll discuss this later.) Name the second ion changing the suffix to –ide.

Examples NaCl Name the metal ion Sodium Name the nonmetal ion, changing the suffix to –ide. Chloride CaO Calcium Oxide Al 2 S 3 AluminumSulfide MgI 2 MagnesiumIodide

Examples BaNa 2 You should recognize a problem with this one This is two metals – not a binary ionic compound Banana The name of this is Banana (haha!!) What is the name of this compound: HIJKLMNO? WATER – “H” to “O” You have to admit – that was funny!

What About The Transition Metals And Using Roman Numerals? How Does That Work? Let’s See. FeO Notice – metal and nonmetal. Name the first ion. Since the first ion is a transition element, you must use a Roman Numeral to represent the charge. How do you know the charge? Deductive reasoning. All compounds are neutral. Oxygen has a -2 charge (group 16) Therefore ….. Iron must have a +2 charge since there is one iron and one oxygen. Iron gets a Roman Numeral (II). Iron(II)Oxide Isn’t this easy and FUN!!!

Cu 2 S Name the first ion. Since it is a transition metal, you must use a Roman Numeral. Which Roman Numeral? The Roman Numeral is the same as the charge of the ion. How do you find the charge? Deductive reasoning! All compounds are neutral Sulfur has a -2 charge (group 16) There are two coppers. Therefore each copper must have a +1 charge for all ions to be neutral Copper(I) Sulfide

MnO 2 Name the first ion. Since it is a transition metal, you must use a Roman Numeral. How do you determine the Roman Numeral? It is the same as the charge. What is the charge of Mn? All compounds are neutral. Oxygen (group 16) has a -2 charge. There are two oxygens and one Mn. Therefore Mn must have a +4 charge for this compound to be neutral. Manganese(IV) oxide

Things You Can Learn From Your Dog!! When it is hot outside, drink lots of water. Take naps.

So Why Must We Use Roman Numerals With Transition Elements? single, definite charges.The metals in groups 1, 2, 3, and 13 have single, definite charges. +1Group 1 metals have a +1 charge. +2Group 2 metals have a +2 charge. +3Groups 3 and 13 metals have a +3 charge. Transition metals may have multiple charges – usually two different positive charges. For example, there are two copper oxide compounds: Cu 2 O and CuO We can’t just say Copper oxide. Which one of these is Copper oxide? We must distinguish these by using a Roman Numeral Cu 2 O Copper I oxide Copper is +1 CuO Copper II oxide Copper is +2

How Do You Write Formulas For Binary Ionic Compounds Given The Name? Two Simple Steps: 1.Write the symbol and charge of each ion 2.Balance the charges by providing subscripts Magnesium chloride Write the symbol and charge of each ion. Mg +2 Cl -1 Balance the charges by supplying subscripts. Subscripts tell how many of each atom is present. You need a second Cl -1 to balance the charges Cl -1 MgCl 2

Iron (III) bromide Write the symbol and charge of each ion. The charge of the iron is provided by the Roman Numeral. Fe +3 Br -1 Balance the charges by supplying subscripts. The subscripts tell how many of each ion is needed to balance the compound. You’ll need three bromine ions to balance the one iron. Br -1 FeBr 3

Aluminum SulfideWrite the symbol and charge of each ion. Al +3 S -2 Balance the charges by supplying subscripts. In this case the charges do not evenly divide into each other. You must find the least common multiple. SIX How many aluminums are needed to arrive at a +6 charge? How many sulfurs are needed to arrive at a -6 charge? 2 3 Al +3 S -2 Al 2 S 3

Writing Formulas a Little Quicker Iron and oxygen combine to form a compound. Iron (Fe) has an oxidation number of 3+. Oxygen (O) has an oxidation number of 2–. Predict the chemical formula of this compound.

Fe 3+ O Writing Formulas a Little Quicker

Mn 4+ P Let’s Try Another One: Manganese (IV) phosphide

Mn 4+ O Let’s Try One More: Manganese (IV) oxide MnO 2

Exit Quiz – Formula for magnesium chloride? MgCl

Murphy's Laws of Science and Technology Logic is a systematic method of coming to the wrong conclusion with confidence.

Exit Quiz – Formula for sodium oxide? Na 2 O 1+2-

Exit Quiz – Name for: Fe 2 O Iron (III) oxide 6-6+

Exit Quiz – Formula for: CrO Chromium (IV) oxide 24 Cr O

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Second Category Of Compounds – Ternary Ionic Compounds. These Compounds Contain At Least One Polyatomic Ion. What is a polyatomic ion? Let’s look at the name to try to understands. ionIt is an ion – that means it has a charge. polyatomicIt is polyatomic – that means it is made of more than one atom. Simple as that!! Let’s look at some examples of polyatomic ions.

CO 3 -2 carbonate This ion is composed of one carbon and three oxygens and the entire group has a charge of -2. Polyatomic ion – Group of atoms that act as a unit and carry a charge. You have a page of other polyatomic ions You will need these for the rest of the year!!!

How Do You Recognize Ternary Ionic Compounds? Composed of two ions in which at least one is a polyatomic ion. There is only one positive polyatomic ion (NH 4 +1 ) Three possible types of Ternary Ionic Compounds: Ammonium + negative ion (nonmetal) Metal (positive ion) + negative polyatomic ion Ammonium + negative polyatomic ion Polyatomic Ion

How Do You Name Ternary Ionic Compounds? Name the first ion. Name the second ion. Isn’t that simple??!! Examples: Na 2 CO 3 Carbonate When you look at this compound you should recognize that this is NOT binary. There are THREE elements present. When you see this, immediately look for a polyatomic ion. Carbonate is present here. Name the first ion. Sodium Name the second ion. carbonate Notice that you do NOT change the suffix – just name the polyatomic ion

Fe(OH) 3 Name the first ion. IronRemember that iron requires a Roman Numeral since it is a transition element. What Roman Numeral should be used? The Roman Numeral comes from the charge of the ion. How do you find the charge of the iron? You know two things: All compounds are neutral. You know the charge of OH (-1) Since there are 3 OH groups, each with a -1 charge, the charge of the iron must be +3 for the compound to be neutral (III) Name the polyatomic ion. hydroxide

NH 4 ClName the first ion. AmmoniumName the second ion.chloride Notice that since the second ion is a nonmetal that, like binary ionic compounds, the suffix of the nonmetal changes to –ide. ( NH 4 ) 3 PO 4 Name the first ion. Name the second ion. Ammoniumphosphate Looks like a monster, but it’s really a pussycat.

Cu 2 SO 4 Name the first ion. Copper You should realize that you need a Roman Numeral since copper is a transition metal. The Roman Numeral is the same as the charge. What is the charge? The charge of sulfate is -2. Since there are two coppers, the charge of the copper must be +1. (I)sulfate Name the second ion.

How Do You Write Formulas For Ternary Ionic Compounds? Very Much Like Writing Formulas For Binary Ionic Compounds. Three Steps: 1.Write the formulas/symbols of each ion. 2.Balance the charges by supplying subscripts. 3.If a subscript is needed for a polyatomic ion, it must be put in parentheses with the subscript on the outside. Let’s do some!!

Aluminum nitrateFirst, you can tell from the name that there is a polyatomic ion present (nitrate). All binary ionic compounds have suffixes of –ide. Write the formula/symbol and charge of each ion. Al 3+ NO 3 -1 Balance the charges by supplying subscripts. Since Al is +3 and NO 3 is -1, you need a total of 3NO 3 -1 to balance one Al +3 Since you will need a subscript of 3 for NO 3 -1, you need to put this in parentheses with the 3 outside. Al(NO 3 ) 3

Lead (IV) acetate Write the formula/symbol and charge of each ion. Pb +4 C 2 H 3 O 2 -1 Balance the charges by supplying subscripts. Since Pb is +4 and C 2 H 3 O 2 is -1, you will need 4 C 2 H 3 O 2 -1 to balance 1Pb +4 Pb(C 2 H 3 O 2 ) 4 Calcium phosphate Write the formula/symbol and charge of each ion. Balance the charges by supplying subscripts. Since Ca is +2 and PO 4 is -3, you will need 3 Ca +2 to balance 2 PO 4 -3 Ca +2 PO 4 -3 Ca 3 (PO 4 ) 2

Exit Quiz  Al 3+ combines with sulfate (SO 4 ) 2– to make aluminum sulfate.  Write the chemical formula for aluminum sulfate.

Al 3+ (SO 4 ) Exit Quiz Answer

Overall Strategy For Naming Chemical Compounds.

Mn 4+ (PO 4 ) Let’s Try Another One: Manganese (IV) phosphate

Mn 4+ (CO 3 ) Let’s Try One More: Manganese (IV) carbonate Mn(CO 3 ) 2

The Third Category of Compounds – Binary Molecular What are Binary Molecular Compounds? These compounds contain two elements (binary). The term “molecular” indicates that these elements are joined by a covalent bond. They must therefore be nonmetals. Bottom line – 2 elements – both nonmetals To name and write formulas for these, you must know some numerical prefixes.

Naming – You Must Use Prefixes. 1 = mono3 = tri 5 = penta 7 = hepta 9 = nona 2 = di4 = tetra 6 = hexa 8 = octa 10 = deca Steps 1.The first nonmetal only gets a numeric prefix when there is more than one. No prefix if there is only one. 2.The second element always gets a numeric prefix and always has a suffix of -ide

CO 2 Carbon dioxide CO Carbon monoxide N2O4N2O4 Dinitrogen tetraoxide H2OH2O Dihydrogen monoxide CCl 4 Carbon tetrachloride Name the first element. Since there is only one, no prefix is needed. The second element always gets a prefix and a suffix of –ide. Name the first element. Since there are two present, the prefix “di” is needed. The second element always gets a prefix and a suffix of –ide.

AlCl 3 What do you think about this one??? Be careful. This is a metal and nonmetal. Always keep your Periodic Table in front of you for reference. You may have been tempted to say “aluminum trichloride”. This is INCORRECT! This is a binary IONIC compound. No prefixes are used. Simply name it aluminum chloride.

Given The Names Of Binary Molecular Compounds, How Do You Write The Formulas? Very easily done!!! The prefixes tell you how to write the formulas. DO NOT CONSIDER CHARGES. NONMETALS ARE ALL NEGATIVE SO TO USE CHARGES DOES NOT WORK!

Silicon dioxide Diphosphorous pentachloride Silicon and oxygen are both nonmetals. The lack of a prefix on silicon means that there is only ONE silicon. The prefix “di” in front of oxide means that there are TWO oxygens. SiO 2 Phosphorous and chloride are both nonmetals. The prefix “di” means that there are TWO phosphorouses (Is that a word?) The prefix “penta” before chlorine means that there are five chlorines. P 2 Cl 5

NO Nitrogen monoxide Nitrogen and oxygen are both nonmetals. The lack of a prefix on nitrogen means only ONE nitrogen. The prefix “mono” on oxygen indicates ONE oxygen. Is this not sooooooo easy!??

Familiar Saying It is fruitless to attempt to indoctrinate a superannuated canine with innovative maneuvers. You can’t teach an old dog new tricks!

A Flow Chart For Naming Binary Compounds

CO 2 Carbon dioxide SO Sulfur monoxide N2O5N2O5 Dinitrogen pentaoxide CF 4 Carbon tetrafluoride SO 3 Sulfur trioxide CO Carbon monoxide B2O3B2O3 Diboron trioxide NF 5 Nitrogen pentafluoride Exit Quiz