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Writing Chemical Writing Chemical FormulasFormulas

General ChemistryGeneral Chemistry

Mrs. Amy NareMrs. Amy Nare

http://chem.pdx.edu/~wamserc/C335W00/gifs/MW2.gif

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ObjectivesObjectives

Distinguish between molecular and ionic Distinguish between molecular and ionic compoundscompounds

Contrast molecular formulas and formula unitsContrast molecular formulas and formula units Use the periodic table to determine the Use the periodic table to determine the

charge on an ioncharge on an ion Define monatomic and polyatomic ion and Define monatomic and polyatomic ion and

name the charges of common polyatomic ionsname the charges of common polyatomic ions Write the formulas and names for binary and Write the formulas and names for binary and

ternary ionic compoundsternary ionic compounds Write formulas and names for molecular Write formulas and names for molecular

compoundscompounds

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Inspiration Concept Inspiration Concept MapMap

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Chemical BondingChemical Bonding

Atoms – same number of protons (+) Atoms – same number of protons (+) and electrons (-); electrically neutraland electrons (-); electrically neutral

Ions – atoms w/ a (+) or (-) charge; Ions – atoms w/ a (+) or (-) charge; have lost or gained electrons (e-)have lost or gained electrons (e-)

* * Cations: (+) charge; has lost e-; Cations: (+) charge; has lost e-; metalsmetals

* Anions: (-) charge; has gained e-;* Anions: (-) charge; has gained e-;

nonmetalsnonmetals

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Chemical BondingChemical Bonding

Types of CompoundsTypes of CompoundsA. A. MolecularMolecular – atoms – atoms

bonded together by shared bonded together by shared pairs of e- (covalent bonds); pairs of e- (covalent bonds); formed between nonmetalsformed between nonmetals

ex: Cex: C66HH1212OO66

B. B. IonicIonic – ions – ions attracted to each other by attracted to each other by opposite charges; formed opposite charges; formed between a metal and a between a metal and a nonmetalnonmetalex: NaClex: NaCl

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Chemical BondingChemical Bonding

CompoundCompound MolecularMolecular IonicIonic

Smallest unitSmallest unit MoleculeMolecule Formula unitFormula unit

Types of Types of elementselements

NonmetalsNonmetals Metal cations Metal cations

Nonmetal Nonmetal anionsanions

Physical state Physical state @ room. temp.@ room. temp.

Solid, gas, or Solid, gas, or liquidliquid

SolidSolid

Boiling pointBoiling point High, >300High, >300ooCC Low, <300Low, <300ooCC

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Chemical BondingChemical Bonding

Chemical FormulasChemical Formulas – show the type and – show the type and number of atoms in smallest unit of number of atoms in smallest unit of substancesubstance

Molecular FormulaMolecular Formula – type and – type and number of atoms joined to form a number of atoms joined to form a moleculemolecule

ex: Cex: C22HH55OHOH

Formula UnitFormula Unit – smallest ratio of ions in – smallest ratio of ions in an ionic compoundan ionic compound

ex: CaFex: CaF2 2

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Representing Chemical Representing Chemical CompoundsCompounds

Law of Definite Proportions – in Law of Definite Proportions – in any sample of a compound, the any sample of a compound, the elements are always combined in elements are always combined in the same proportionsthe same proportions

ex: Hex: H22O and HO and H22OO22

HH22O – water – H:O ratio always 2:1O – water – H:O ratio always 2:1

HH22OO22 – hydrogen peroxide – H:O – hydrogen peroxide – H:O ratio always 1:1 ratio always 1:1

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Identifying Ionic Identifying Ionic ChargesCharges Group A elementsGroup A elements – use the – use the

periodic table to determine ionic periodic table to determine ionic chargecharge

* elements in same group have* elements in same group have same ionic chargesame ionic charge

* Group 4A and Noble gases – * Group 4A and Noble gases – almost never form ionsalmost never form ions Group B elementsGroup B elements – many have – many have

more than one ionic chargemore than one ionic charge

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Identifying Ionic Identifying Ionic ChargesCharges

http://wps.prenhall.com/wps/media/objects/476/488316/ch04.htmlhttp://wps.prenhall.com/wps/media/objects/476/488316/ch04.html

Charge on cations corresponds to group #.Charge on cations corresponds to group #.Charge on anions is found by subtracting 8 by group numberCharge on anions is found by subtracting 8 by group number the number 8 is used b/c it represents # of valence e- in Noble the number 8 is used b/c it represents # of valence e- in Noble

gasesgases

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Naming Cations and AnionsNaming Cations and Anions

Monatomic IonsMonatomic Ions Ions formed by one elementIons formed by one element CationsCations

* for Group A elements – just write * for Group A elements – just write element’s name element’s name

ex: calcium ion (Caex: calcium ion (Ca2+)2+) = calcium = calcium * for Group B elements – write element’s* for Group B elements – write element’s

name, then Roman numerals in name, then Roman numerals in parentheses to denote chargeparentheses to denote charge

ex: Feex: Fe2+2+ = Iron (II) and Fe = Iron (II) and Fe3+3+ = Iron (III) = Iron (III) AnionsAnions – drop the end of the element’s – drop the end of the element’s

name & add “–ide” endingname & add “–ide” endingex: chlorine ion (Clex: chlorine ion (Cl1-1-) = chlor) = chlorideide

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Naming Cations and Naming Cations and AnionsAnions

Polyatomic IonsPolyatomic Ions Ions formed by Ions formed by more than onemore than one type of type of

elementelement Atoms of different elements held together Atoms of different elements held together

by covalent bondsby covalent bonds Atoms always stay together and Atoms always stay together and

collectively have a single chargecollectively have a single charge Do Do notnot always have “-ide” ending always have “-ide” ending

ex: NHex: NH441-1- = ammonium ion = ammonium ion

COCO332-2- = carbonate ion = carbonate ion

Learn names, formulas, and charges of Learn names, formulas, and charges of polyatomic ions!polyatomic ions!

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Naming Cations and Naming Cations and AnionsAnions

Potassium ionPotassium ion Copper (II) ionCopper (II) ion Chloride ionChloride ion Oxide ionOxide ion BaBa2+2+

SS2-2-

AuAu3+3+

Nitrite ionNitrite ion Hydroxide ionHydroxide ion Phosphate ionPhosphate ion SOSO44

2-2-

CrOCrO442-2-

ClOClO332-2-

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Binary Ionic Binary Ionic CompoundsCompounds Compounds composed of 2 different Compounds composed of 2 different

monatomic elementsmonatomic elements To write binary formulas – write cation first, To write binary formulas – write cation first,

then anionthen anion*criss-cross charges to determine how*criss-cross charges to determine how

many of each ion you needmany of each ion you need *use subscripts to denote number of ions*use subscripts to denote number of ions ex: Caex: Ca2+2+ + Cl + Cl1-1- CaCl CaCl22

NaNa1+1+ + Cl + Cl1-1- NaCl NaCl To name binary compounds – write name of To name binary compounds – write name of

cation first, then anion (-ide)cation first, then anion (-ide)ex: CaClex: CaCl22 = calcium chloride = calcium chloride

LiLi22O = lithium oxideO = lithium oxide

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Ternary Ionic Ternary Ionic CompoundsCompounds Compounds containing at least one polyatomic ion; at least 3 Compounds containing at least one polyatomic ion; at least 3

different elementsdifferent elements To write ternary formulas: write cation first, then anionTo write ternary formulas: write cation first, then anion *criss-cross charges to determine how*criss-cross charges to determine how many of each ion you needmany of each ion you need *use subscripts to denote number of ions*use subscripts to denote number of ions

**mustmust use parentheses around polyatomic if more than one use parentheses around polyatomic if more than one isis

needed!!!needed!!!ex: Naex: Na1+1+ + SO + SO33

2-2- Na Na22SOSO33

MgMg2+2+ + OH + OH1-1- Mg(OH) Mg(OH)22 [not same as MgOH [not same as MgOH22]] To name ternary compounds: write name of cation, then name To name ternary compounds: write name of cation, then name

of anion (not all end in “-ide”) of anion (not all end in “-ide”) **be careful with transition metals (more than one charge)****be careful with transition metals (more than one charge)**ex: CaCOex: CaCO33 = calcium carbonate = calcium carbonate

PbSOPbSO44 = lead (II) sulfate = lead (II) sulfateAgAg22CrOCrO44 = silver chromate = silver chromate

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Ionic CompoundsIonic Compounds

NaNONaNO33

CaSOCaSO44

(NH(NH44))22OO

CuSOCuSO33

Fe(OH)Fe(OH)33

NaFNaF

Lithium sulfideLithium sulfide Iron (III) phosphideIron (III) phosphide Magnesium fluorideMagnesium fluoride Barium nitrateBarium nitrate Aluminum Aluminum

hydroxidehydroxide Potassium Potassium

phosphatephosphatePractice making ionic compounds!

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Binary Molecular Binary Molecular CompoundsCompounds

Two nonmetals joined by covalent bondsTwo nonmetals joined by covalent bonds Use prefixes for namingUse prefixes for naming

1 = mono-2 = di-3 = tri-4 = tetra-5 = penta-

6 = hexa-7 = hepta-8 = octa-9 = nona-10 = deca-

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Binary Molecular Binary Molecular CompoundsCompounds To name binary molecular compounds: To name binary molecular compounds:

*first element gets a prefix if there is more *first element gets a prefix if there is more than onethan one*second element ALWAYS gets prefix, and “-*second element ALWAYS gets prefix, and “-ide” endingide” endingex: Nex: N22OO33 = dinitrogen trioxide = dinitrogen trioxide

CO = carbon monoxide (CO = carbon monoxide (notnot monocarbon)monocarbon)

If element begins with vowel and prefix ends in If element begins with vowel and prefix ends in “a” or “o”, then drop last vowel on prefix to “a” or “o”, then drop last vowel on prefix to form the nameform the name

ex: Clex: Cl22OO77 = dichlorine heptoxide ( = dichlorine heptoxide (notnot heptaoxide)heptaoxide)

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Molecular CompoundsMolecular Compounds

PP22OO55

NN22OO

NONO22

CBrCBr44

COCO22

tetraiodine tetraiodine nonoxidenonoxide

sulfur hexafluoridesulfur hexafluoride nitrogen trioxidenitrogen trioxide carbon tetrahydridecarbon tetrahydride phosphorus phosphorus

trifluoridetrifluoride

2020

Assess what you learned. Log on Assess what you learned. Log on to the Internet and take the quiz.to the Internet and take the quiz.

http://school.discovery.com/quizzes31/amy_trauth/Forhttp://school.discovery.com/quizzes31/amy_trauth/FormulasQuiz.htmlmulasQuiz.html

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Websites on Writing Websites on Writing FormulasFormulas

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Review

Fordham Preparatory School Online Chemistry 8 6 6 8 7 35 6.6

This website by Greg Curran at Forham Prep is an online resource that includes lecture notes, labs, worksheets, quizzes, and links to other useful sites. Website is fairly current and thoughtfully designed, making it easy to navigate and find necessary information quickly.

University of North Carolina - Chapel Hill Chemistry

Fundamentals Program 5 7 5 4 4 25 5.0

A very basic website that outlines some fundamental concepts in general chemistry. Very few links to other websites are provided. Website has not been updated since 1998. Overall design is lacking and content is satisfactory for a university. This site does provide some interactive activities that could be useful for students to practice skills.

General Chemistry Online, Frostburg State University 8 6 10 7 7 38 7.6

This website designed for general chemistry undergrads clearly indicates objectives of lessons, provides pre-tests and post-tests, and short, but informative narratives to explain major concepts. Graphics are are clear and useful, mostly line drawings and molecular representations of compounds. Fred Senese is co-author of a general chemistry textbook for undergrads, making him a well-known authority on the subject.

ScienceGeek.net 8 7 8 9 6 38 7.6

The Chemistry Pages on this website gives high school chemistry students access to PowerPoint notes, labs, and worksheets. Some interactive activities are also provided for students to review major concepts. Few graphics are provided, but this fact does not detract from the utility of the website. The site is nicely designed and easy to navigate. All the links tested were functional.

General Chemistry, Purdue University 5 6 7 8 6 32 6.4

Designed as a tutorial for undergrad chemistry students, this website provides many useful tools and interactive activities to help students grasp key concepts. Many unique features, such as a molecular library that shows the shape and bonding patterns of over 400 different molecules. Many practice problems on the nomenclature of inorganic compounds. Joint authorship by some students ans faculty in the Department of Chemistry.

Chem Team 4 5 5 8 8 30 6.0

This website, written for high school chemistry students, has most of the general topics covered elswhere. However, the author provides links to many other sites on the subject and provides nice tutorials for practice and review. Few graphics are provided, but are educational when present. Information on author's background and links to his credentials are difficult to locate. Page design is simple, logical, and satisfactory in its design.

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