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Key Question: Why Do Atoms Combine In Certain Ratios?

Key Question: Why Do Atoms Combine In Certain Ratios?. Review of Oxidation Numbers. Review of Oxidation Numbers. All compounds have an electrical charge of zero (they are neutral).

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Key Question: Why Do Atoms Combine In Certain Ratios?

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  1. Key Question: Why Do Atoms Combine In Certain Ratios?

  2. Review of Oxidation Numbers

  3. 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.

  4. 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?

  5. H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar 1 2 3 4 5 6 7 8 Valence Electrons ------------------------ The Number Of Electrons In The Outside Shell.

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

  7. Ionic Bonds On the periodic table, strong electrondonorsare 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.

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

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

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

  11. Naming Compounds and Writing Formulas

  12. 6 Types Of Chemical Compounds • Binary ionic - metal ion – nonmetal ion • Binary molecular - two nonmetals • Ternary ionic - at least one ion is a polyatomic ion • Binary acid - H – nonmetal • Ternary acid - H – Polyatomic ion • Base - metal ion – OH

  13. 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. • Remember that metals (except Hydrogen) are found to the left of the stairstep on the Periodic Table. • Nonmetals are found on the right side of the stairstep of the Periodic Table. • Metalloids are the 7 elements on or below the stairstep except Al and At. For naming purposes they will tend to behave like nonmetals.

  14. Naming Binary Compounds A binary ionic compoundis held together by ionic bonds. Binary molecular compoundsconsist of covalently bonded atoms. Each type of compound has its own naming rules.

  15. How Do You Name Binary Ionic Compounds? • (Composed Of Two Elements – A Metal And A Nonmetal) • Name the first ion • From groups 1, 2, 3, 13, zinc, cadmium, or silver. (You must use a Roman Numeral with the name for the other metals – we’ll discuss this later.) • Name the second ion changing the suffix to –ide.

  16. Naming Binary Ionic Compounds MgBr2 is magnesium(name of first element) + brom(root name of second element) + idesuffix = magnesium bromide

  17. Examples This is two metals – not a binary ionic compound BaNa2 You should recognize a problem with this one 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!

  18. Exit Quiz NaCl Sodium Chloride Name the metal ion CaO Name the nonmetal ion, changing the suffix to –ide. Oxide Calcium Al2S3 Aluminum Sulfide MgI2 Magnesium Iodide

  19. What About The Transition Metals And Using Roman Numerals? How Does That Work? Let’s See. Notice – metal and nonmetal. FeO Name the first ion. Since the first ion is a transitionelement, you must use a Roman Numeral to represent the charge. Iron (II) Oxide 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). Isn’t this easy and FUN!!!

  20. 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 the compound to be neutral Cu2S Copper (I) Sulfide

  21. MnO2 • 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? • Oxygen (group 16) has a -2 charge and a total of -4 charge. • There are two oxygens with one manganese. • Therefore Mn must have a +4 charge for this compound to be neutral. Manganese (IV) oxide

  22. Things You Can LearnFrom Your Dog!! • When it is hot outside, drink lots of water. • Take naps.

  23. So Why Must We Use Roman Numerals With Transition Elements? • The metals in groups 1, 2, 3, and 13 have single, definite charges. • Group 1 metals have a +1 charge. • Group 2 metals have a +2charge. • Groups 3 and 13 metals have a +3charge. • Transition metals may have multiple charges – usually two different positive charges. • For example, there are two copper oxide compounds: Cu2O Copper (I) oxide Copper is +1 CuO Copper (II) oxide Copper is +2 Cu2O 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

  24. And Remember, There Are Three Transition Elements Which Do Not Require A Roman Numeral Because They Have Single Definite Charges. These Are: Zinc – Zn2+ Cadmium – Cd2+ Silver – Ag+ You need to remember the charges for these. Ag2O Name the first ion. Name the second ion changing the suffix to –ide. Silver oxide No Roman Numerals needed for these. ZnCl2 Name the first ion. Zinc chloride Name the second ion changing the suffix to –ide.

  25. How Do You Write Formulas For Binary Ionic Compounds Given The Name? • Two Simple Steps: • Write the symbol and charge of each ion • Balance the charges by providing subscripts Magnesium chloride Write the symbol and charge of each ion Mg2+ Cl- Balance the charges by supplying subscripts. Subscripts tell how many of each atom is present. Cl- MgCl2 You need a second Cl-1 to balance the charges

  26. Iron (III) bromide Fe3+ Br - Write the symbol and charge of each ion. The charge of the iron is provided by the Roman Numeral. Br - Br - FeBr3 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.

  27. Aluminum Sulfide Write the symbol and charge of each ion. Al3+ S2- Balance the charges by supplying subscripts. Al3+ S2- In this case the charges do not evenly divide into each other. You must find the least common multiple. SIX S2- Al2S3 How many aluminums are needed to arrive at a +6 charge? 2 How many sulfurs are needed to arrive at a -6 charge? 3

  28. 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.

  29. Writing Formulas a Little Quicker 2- 3+ Fe O 2 3

  30. Let’s Try Another One: Manganese (IV) phosphide 3- 4+ Mn P 3 4

  31. Let’s Try One More: Manganese (IV) oxide 2- 4+ Mn O 2 4 MnO2

  32. Exit Quiz – Formula for magnesium chloride? 2+ 1- MgCl2

  33. Exit Quiz – Formula for sodium oxide? 1+ 2- Na2O

  34. Exit Quiz – Name for: 6+ 6- 3+ 2- Fe2O3 Iron (III) oxide

  35. Exit Quiz – Formula for: 4+ 2- Chromium (IV) oxide Cr O 2 4 CrO2

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

  37. The Second 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.

  38. Naming – You Must Use Prefixes. • 1 = mono 3 = tri 5 = penta 7 = hepta 9 = nona • 2 = di 4 = tetra 6 = hexa 8 = octa 10 = deca • Steps • The first nonmetal only gets a numeric prefix when there is more than one. No prefix if there is only one. • The second element always gets a numeric prefix and always has a suffix of -ide

  39. Naming Binary Molecular Compounds As with binary ionic compounds, the ending of the name of the second element in the compound is modified by adding the suffix –ide.

  40. Familiar Saying Socially orientated individuals tend to congregate in gregariously homogenous groupings. Birds of a feather flock together!!

  41. CO2 Carbon dioxide CO Carbon monoxide N2O4 Dinitrogen tetraoxide H2O Dihydrogen monoxide CCl4 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.

  42. 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. AlCl3

  43. 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!

  44. Silicon dioxide 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. SiO2 Diphosphorous pentachloride 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. P2Cl5

  45. 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. NO Is this not sooooooo easy!??

  46. A Flow Chart For Naming Binary Compounds

  47. Exit Quiz CO2 Carbon dioxide SO Sulfur monoxide N2O5 Dinitrogen pentaoxide CF4 Carbon tetrafluoride SO3 Sulfur trioxide CO Carbon monoxide B2O3 Diboron trioxide NF5 Nitrogen pentafluoride

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