1 / 11

I. Molecules and Ions Chemical Bonds Forces that hold atoms together

I. Molecules and Ions Chemical Bonds Forces that hold atoms together Molecules = collections of atoms that form a new substance (compound) Covalent Bond = sharing of electron pairs between two atoms Chemical Formula = representation of a molecule showing the number and type of atoms

arnaud
Download Presentation

I. Molecules and Ions Chemical Bonds Forces that hold atoms together

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. I. Molecules and Ions • Chemical Bonds • Forces that hold atoms together • Molecules = collections of atoms that form a new substance (compound) • Covalent Bond = sharing of electron pairs between two atoms • Chemical Formula = representation of a molecule showing the number and type of atoms • CO2 has one carbon atom and two oxygen atoms • NH3 has one nitrogen atom and three hydrogen atoms • Structural Formula = representation of a molecule showing individual chemical bonds as lines • Normal lines are taken to be in the plane of the page • Dashed lines are taken to go back behind the plane of the page • Wedged line are taken to go forward in front of the plane of the page

  2. Ionic Bond = attraction between oppositely charged ions • Ion = charged atom of group of atoms NH4+ or NO3- (polyatomic ions) • Cation = ion with a positive charge Na - e- -------> Na+ • Anion = ion with a negative charge Cl + e- -------> Cl- • Such a compound (like NaCl) is called a Salt or an Ionic Solid C Cl-

  3. II. Nomenclature • The need for a system • Early chemists named new compounds however they wished • Examples: quicklime, milk of magnesia, laughing gas • A system for naming makes it easier for chemists to communicate about the more than 5 million known chemical compounds • Type I Binary Ionic Compounds • 1. Binary ionic compounds are composed of 2 elements only (cation + anion) • Salts where the cation can have only one possible oxidation state are type I. These are H+ and the Group I-III metals • Rules • Cation comes first and anion second • Cation keeps the name of its element • Anion changes the element name to an –ide ending • Examples • a. NaCl = sodium chloride b. Li2O = lithium oxide • CaS = calcium sulfide d. MgBr2 = magnesium bromide

  4. C. Type II Binary Ionic Compounds • Cations that can have multiple oxidation states require more specificity. These are usually the transition metal cations. • The charge on the metal ion is given as a Roman Numeral in parentheses • Examples • CuCl = copper(I) chloride b. HgO = mercury(II) oxide • Fe2O3 = iron(III) oxide c. MnO2 = manganese(IV) oxide • Determining the oxidation state of the cation • Use the location of the anion to determine its negative charge • Group 7 = -1, Group 6 = -2, Group 5 = -3 • Assign the appropriate cation charge to make a neutral compound • Examples • Ionic Compounds with Polyatomic Ions • Polyatomic ions have special names that must be memorized • Hg22+ (mercury(I)) and NH4+ (ammonium) are the only common cations • Many common anions are polyatomic • There can be several different oxyanions in a series • –ite is the anion with less oxygens; -ate is the one with more • More than two in a series: hypo- means less; per- means more • Hypochlorite (ClO-), Chlorite (ClO2-), Chlorate (ClO3-), Perchlorate (ClO4-)

  5. Common Polyatomic Ions • E. Hydrated Ionic Compounds • CaSO4 • 0.5H2O calcium sulfate hemihydrate • BaCl2 • 6H2O barium chloride hexahydrate • CuSO4 • 5H2O copper(II) sulfate pentahydrate • mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa- • nona-, deca-

  6. F. Binary Covalent Compounds • Formed between two nonmetals • Rules • Name elements in order as they appear in the formula • Name the first element using its full element name (don’t use –ide) • Name the second element using the –ide ending • Modify the element names with a prefix for how many atoms present • Don’t use mono- for the first element • Examples • N2O = dinitrogen monoxide b. NO = nitrogen monoxide • NO2 = nitrogen dioxide d. N2O3 = dinitrogen trioxide • G. Formulas from names are even more important at this stage • vanadium(V) fluoride = ? • dioxygen difluoride = ? • rubidium peroxide = ? • gallium oxide = ?

  7. H. Naming Acids • Acid = compound that produces H+ when dissolved in water • Think of them as H+ ions attached to anions • When the anion doesn’t contain O, name as hydro_____ic acid • HCl = hydrochloric acid • HCN = hydrocyanic acid • H2S = hydrosulfuric acid • When the anion does contain O, this is an oxyacid • If the anion would be named –ate, then name the acid –ic acid • H2SO4 = sulfuric acid • H3PO4 = phosphoric acid • HNO3 = nitric acid • If the anion would be named –ite, then name the acid –ous acid • H2SO3 = sulfurous acid • HNO2 = nitrous acid

  8. III. Molar Mass • A. The molar mass is the mass in grams of one mole of a compound • B. The relative weights of molecules can be calculated from atomic masses • 1. Water = H2O = 2(1.008 g/mol) + 16.00 g/mol = 18.02 g/mol • 2. 1 mole of H2O will weigh 18.02 g, therefore the molar mass of H2O is 18.02 g • 3. 1 mole of H2O will contain 16.00 g of oxygen and 2.02 g of hydrogen • C. Calculations with molar mass • 1. Example: Juglone = C10H6O3 Find Molar mass and # moles in 0.0156 g • 2. Example: How many molecules of isopentyl acetate (C7H14O2) and how many carbon atoms are released in one bee sting (1 mg)?

  9. D. Mass Percent • Composition of a substance can be given multiple ways • Molecular formula gives ratio of the number of each element • The Mass Percent gives the composition by mass of each element • Example: Ethanol, C2H6O has a molar mass of 46.07 g • Example: Determine the Mass Percent of C14H20N2SO4.

More Related