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BLB – Chapter 2 Atoms, Molecules, and Ions Note: Many images are from “Chemistry, The Central Science”, 9th Ed., by Brown, LeMay, and Bursten. Atoms - smallest unit in a reaction - building blocks of elements Molecules - building blocks of compounds Ions - building blocks of ionic compounds. Dalton’s atomic theory - 4 postulates - basic grammar of chemistry #1. Provides the definition of atom #2. Explains the identity of atom #3. Explains the Law of conservation of atoms in a chemical reaction #4. Explains an atom’s function in compound formation Discovery of the subatomic particles e-, p+,no location Electrons Protons Neutrons mass charge Radioactivity – why does it happen? Alpha, a, particles, 42He2+: mass = 4 amu charge = 2+ Beta, b, particles, 0–le: mass = 0.00055 amu charge = 1– Gamma, g, particles: photons with no mass or charge Modern view of atomic structure: Particle Proton Neutron Electron Charge 1+ None 1– Mass (amu) 1.0073 1.0087 5.486 x 10–4 Isotopes Name hydrogen, 1H deuterium, 2H tritium, 3H Proton 1 1 1 Electron 1 1 1 Neutron 0 1 2 Atomic number, Z: (no. of p+) Mass number, A: (no. of p+ + no. of no) Nuclear symbol, A Z X # neutron = mass # (A) – atomic # (Z) Problem 17. Fill in the gaps in the following table, assuming each column represent a neutral atom. Symbol Protons Neutrons Electrons Mass# 52Cr ? ? ? ? 32 42 ? ? ? ? 20 20 ? ? ? ? 86 222 ? 77 ? ? 193 Atomic weights: Atomic mass scale 1 amu = 1.66054 x 10–24 g 1 g = 6.02214 x 1023 amu Average atomic weight and Isotopic abundance Problem 23. Pb consists of four naturally occurring isotopes with masses (amu): 203.97302; 1.4% abundance 205.97444; 24.1% abundance 206.97587; 22.1 % abundance 207.97663; 52.4% abundance Calculate the average atomic weight of lead. The periodic table (rows and columns) Color codes in the periodic table Characteristics of: Metals Nonmetals Metalloids Main group elements Alkali metals Alkaline earth metals Noble gases Halogens Chalcogens Transition metals - Problem 31. For each of the following elements, write its chemical symbol determine the name of the group to which it belongs, and indicate whether it is a metal, metalloid, or nonmetal Element a) b) c) d) e) Potassium Iodine Magnesium Argon Sulfur Symbol Group nonmetal metalloid or Metal Molecules and chemical formulas – Molecular and empirical formulas – Molecular formula and structural formula – Problem 37. How many hydrogen atoms are there in each of the following? a) C2H5OH b) Ca(CH3COO)2 c) (NH4)3PO4 Problem 41. Write the empirical formula corresponding to each of the following molecular formulas: a) Al2Br6 b) C3H8 c) C4H8O2 d) P4O10 e) C6H4Cl2 f) B3N3H6 Ions and ionic compounds – Cations – positively charged ions. (Other characteristics?) Anions – negatively charged ions. (Other characteristics?) Monatomic ion – only one atom in the species. (Consult the periodic table.) Polyatomic ion – more than one atom in the species. (Memorize the list on Table 2.5.) Problem 43. Predict the charge of the monatomic ion of each, using a periodic table: a) Al b) Ca c) S d) Cs How to write the chemical formulas of ionic compounds? – cations followed by anions – cross over of the charges as subscripts Mg 2+ N 3- Mg3N2 Problem 45. Using the periodic table to guide you, predict the formula and name of the compound formed by the following elements: Elements a) Ga and F b) Li and H c) Al and I d) K and S Formula Name Problem 47. Predict the empirical formula for the ionic compound formed by a) Ca2+ and Br– b) NH4+ and Cl– c) Al3+ and C2H3O2– d) K+ and SO42– e) Mg2+ and PO43– Problem 49. Predict whether each of the following compounds is molecular or ionic: a) B2H6 b) CH3OH c) LiNO3 d) Sc2O3 e) CsBr f) NOCl g) NF3 h) Ag2SO4 Naming inorganic ionic compounds Cations: - Names are the same as the metals, end in “-ium”. Consult Table 2.4. - If multiple charges are possible, use Roman numeral to indicate the charge. Fe2+ is iron(II) or ferrous Fe3+ is iron(III) or ferric Common in transition and post transition metals. An important polyatomic cation is NH4+ (ammonium) Anions: - Monatomic ions stem name plus “-ide” H– is hydride N3– is nitride. - Polyatomic anions containing oxygen (called oxyanions) have names ending with “-ate” or “ite”. NO2– nitrite NO3– is nitrate. Anions: - With halogens, oxyanions use prefixes of “per-” “hypo-” ClO4– is perchlorate ClO3– is chlorate ClO2– is chlorite ClO– is hypochlorite. - Anions: - adding H+ to an oxyanion add the prefix “hydrogen” of “dihydrogen”. HCO3– is hydrogen carbonate (or bicarbonate), H2PO4– is dihydrogen phosphate. Consult Table 2.5.- Naming ionic compounds – The name of the cation is followed by the name of the anion. CaCl2 is calcium chloride, Cu(ClO4)2 is copper(II) perchlorate (or cupric perchlorate). Names and formula of acids –formulas start with a hydrogen atom. a. Acids based on anions whose names end with –ide: “hydro-” as prefix and “-ic” as ending. HCl is hydrochloric acid H2S is hydrosulfuric acid. b. Acids based on anions whose names end with –ate or –ite: “--”ate” anion ends in “-ic” as an acid SO42- ; H2SO4 “-ites” anions ends in “-ous” as an acid SO32- ;H2SO3 Naming binary molecular compounds –contain only two types of atoms. - element farthest to the left in the periodic table usually is written first. The more electronegative atom comes second and ends in “ide”. - for elements in the same group, the lower one is named first. More electronegative atom comes second and ends in –“ide” - Greek prefixes are used to indicate the number of atoms of each element. 1 = mono, 2 = di, 3 = tri, 4 = tetra, 5 = penta, 6 = hexa, 7 = hepta, 8 = octa, 9 = nona, 10 = deca Problem 51. Write the chemical formula for a) chlorite ion b) chlorate ion c) perchlorate ion d) hypochlorite ion Problem 53. Write the chemical name of the following ionic compounds. Chemical formula Chemical name a) AlF3 b) Fe(OH)2 c) Cu(NO3)2 d) Ba(ClO4)2 e) Li3PO4 f) Hg2S g) Ca(C2H3O2)2 h) Cr2(CO3)3 i) K2CrO4 j) (NH4)2SO4 Problem 55. Write the chemical formulas of the following compounds. Chemical name a) copper(I) oxide b) Potassium peroxide c) Aluminum hydroxide d) Zinc nitrate e) Mercury(I) bromide f) Iron(III) carbonate g) Sodium hypobromite Chemical formula Problem 57. Write the chemical formula or name, as appropriate, for each of the following acids: Chemical formula HBrO3 HBr H3PO4 ………………… ………………… ………………… Chemical name ………………… ..……………….. ………………… Hypochlorous acid Iodic acid Sulfurous acid Problem 59. Write the chemical name or formula, as appropriate, for the following molecular substances: Chem. formula Chem. Name SF6 ………………………………… IF3 ………………………………… XeO3 ………………………………… ……………. Dinitrogen tetroxide …………….. Hydrogen cyanide …………….. Tetraphosphorus hexasulfide Problem 61. Write the chemical formula of each substance mentioned in the following word descriptions. a) Zinc carbonate can be heated to form zinc oxide and carbon dioxide. b) On treatment with hydrofluoric acid silicon dioxide forms silicon tetrafluoride and water. c) Sulfur dioxide reacts with water to form sulfurous acid. d) The substance hydrogen phosphide, commonly called phosphine, is a toxic gas. e) Perchloric acid reacts with cadmium to form cadmium(II) perchlorate. f) Vanadium(III) bromide is a colored solid. Problem 76. The element oxygen has three naturally occurring isotopes, with 8, 9, and 10 neutrons in the nucleus, respectively. a) Write the full chemical symbols for these three isotopes. b) Describe the similarities and differences between the three kinds of atoms of oxygen. Problem 87. Name each of the following oxides. Assuming that the compounds are ionic, what charge is associated with the metallic element in each case? Formula a) NiO b) MnO2 c) Cr2O3 d) MoO3 Chemical name Charge on the metal atom Problem 90. Write the chemical names and formula of the following substances: Common name a) Table salt b) Smelling salt b) Baking soda b) Washing soda b) Caustic soda b) Caustic potash b) Plaster of Paris b) Muriatic acid b) Battery acid Chemical name Chemical formula