University:
Kentucky State University
Course:
CHE 101 | General Chemistry I
Academic year:

2019
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205

Pages:

62
Author:

andalus3q5

Elements, Compounds, and the Periodic Table Periodic Table Modern Periodic Table ▪ Arranged by increasing atomic number (Z ): ▪ Rows called periods ▪ Columns called groups or families ▪ Identified by numbers ▪ 1 – 18 standard international ▪ 1A – 8A longer columns and 1B – 8B shorter columns 2 Modern Periodic Table with group labels and chemical families identified Note: Placement of elements 58 – 71 and 90 – 103 saves space 3 Representative/Main Group Elements A groups—Longer columns ▪ Alkali Metals ▪ 1A = first group ▪ All are metals except for H ▪ Tend to form +1 ions 4 Representative/Main Group Elements A groups—Longer columns ▪ Alkaline Earth Metals ▪ 2A = second group ▪ Tend to form +2 ions 5 Representative/Main Group Elements A groups—Longer columns ▪ Halogens ▪ 7A = next to last group on right ▪ Form diatomic molecules in elemental state ▪ 2 gases – F2, Cl2 ▪ 1 liquid – Br2 ▪ 2 solids – I2, At2 ▪ Form –1 ions with alkali metals—salts (e.g. NaF, NaCl, NaBr, and NaI) 6 Representative/Main Group Elements A groups—Longer columns ▪ Noble Gases ▪ 8A = last group on right ▪ Inert—very unreactive ▪ Only heavier elements of group react and then very limited ▪ Don’t form charged ions ▪ Monatomic gases (e.g., He, Ne, Ar) 7 Transition Elements B groups—shorter columns ▪ All are metals ▪ In center of table ▪ Begin in fourth row ▪ Tend to form ions with several different charges e.g., ▪ Fe2+ and Fe3+ ▪ Cu+ and Cu2+ ▪ Mn2+, Mn3+, Mn4+, Mn5+, Mn6+, and Mn7+ 8 Metals, Nonmetals, or Metalloids ▪ Elements break down into three broad categories ▪ Organized by regions of periodic table Metals ▪ Left-hand side ▪ Sodium, lead, iron, gold Nonmetals ▪ Upper right-hand corner ▪ Oxygen, nitrogen, chlorine Metalloids ▪ Diagonal line between metals and nonmetals ▪ Boron to astatine 9 Metals, Nonmetals, or Metalloids 10 Your Turn! Classify the following three elements as a metal, non-metal, or metalloid: silicon (Si), vanadium (V), bromine (Br) A. nonmetal, metal, nonmetal, respectively B. metal, metalloid, nonmetal, respectively C. nonmetal, metal, metalloid, respectively D. metalloid, metal, metalloid, respectively E. None of these are correct 11 Your Turn! Strontium (Sr) is a _______, ruthenium (Ru) is a ________, and iodine (I) is a_________. A. alkali metal, transition metal, halogen B. transition metal, alkaline earth metal, halogen C. alkaline earth metal, transition metal, halogen D. transition metal, alkali metal, noble gas E. alkali metal, actinide, halogen 12 Your Turn! Which of the following statements is correct? A. Cu is a representative transition element B. Na is an alkaline earth metal C. Al is a metalloid in group 3A D. F is a representative halogen E. None of these are correct 13 Molecules and Chemical Formulas ▪ Atoms combine into compounds ▪ Useful to visualize atoms, compounds, and molecules ▪ Atoms represented by spheres ▪ Different atoms have different colors ▪ Standard scheme is represented on the right 14 Molecules ▪ Atoms combine to form more complex substances ▪ Discrete particles ▪ Each composed of two or more atoms e.g., ▪ Molecular oxygen, O2 ▪ Carbon dioxide, CO2 ▪ Ammonia, NH3 ▪ Sucrose, C12H22O11 15 Depicting Molecules ▪ Want to show: ▪ Order in which atoms are attached to each other ▪ 3-dimensional shape of molecule ▪ Three ways of visualizing molecules: 1. Structural formula 2. Ball-and-stick model 3. Space filling model 16 Chemical Reactions ▪ When one or more substances react to form one or more new substances e.g., Reaction of methane, CH4, with oxygen, O2, to form carbon dioxide, CO2, and water, H2O. Reactants = CH4 and O2 Products = CO2 and H2O ▪ How to depict? ▪ Words too long ▪ Pictures too awkward 17 Balanced Chemical Equation Ex. 2C4H10 + 13O2  8CO2 + 10H2O 4 C and 10 H per molecule Subscripts 2 O per molecule 2 H and 1 O 1 C and 2 per molecule O per molecule ▪ Define identity of substances ▪ Must not change when equation is balanced 18 Balanced Chemical Equation Ex. 2C4H10 + 13O2  8CO2 + 10H2O 2 molecules of C4H10 13 molecules 8 molecules of O2 of CO2 10 molecules of C4H10 Coefficients ▪ Number in front of formulas ▪ Indicate number of molecules of each type ▪ Adjusted so number of each type of atom is same on both sides of arrow ▪ Can change 19 Balanced Chemical Equations ▪ How do you determine if an equation is balanced? ▪ Count atoms ▪ Same number of each type on both sides of equation? ▪ If yes, then balanced ▪ If no, then unbalanced Ex. 2C4H10 + 13O2  8CO2 + 10H2O Reactants Products 2×4 = 8 C 8×1 = 8 C 2×10 = 20 H 10×2 = 20 H 13×2 = 26 O (8×2)+(10×1)= 26 O 20 Learning Check Fe(OH)3 + 2 HNO3  Fe(NO3)3 + 2 H2O Reactants Fe 1 Products 1 O 3 + (2×3) = 9 (3×3) + 2 = 11 H 3+2=5 (2×2) = 4 N 2 3 ▪ Not balanced ▪ Only Fe has same number of atoms on either side of arrow. 21 Your Turn! How many atoms of each element appear on each side of the arrow in the following equation? 4NH3 + 3O2 → 2N2 + 6H2O Reactants Products N (4 × 1) = 4 (2 × 2) = 4 O (3 × 2) = 6 (6 × 1) = 6 H (4 × 3) = 12 (6 × 2) = 12 22 Your Turn! Count the number of atoms of each element on both sides of the arrow to determine whether the following equation is balanced. 2(NH4)3PO4 + 3Ba(C2H3O2)2 → Ba3(PO4)2 + 6NH4C2H3O2 H Reactants N (2 × 3) = 6 Products (6 × 1) = 6 (2×3×4)+(3×3×2) = 42 O (2×4) + (3×2×2) = 20 (6×4) + (6×3) = 42 (2×4) + (6×2) = 20 P (2 × 1) = 2 (2 × 1) = 2 Ba (3 × 1) = 3 (3 × 1) = 3 23 Ions and Ionic Compounds Ions ▪ Transfer of one or more electrons from one atom to another ▪ Form electrically charged particles Ionic compound ▪ Compound composed of ions ▪ Formed from metal and nonmetal ▪ Infinite array of alternating Na+ and Cl– ions Formula unit ▪ Smallest neutral unit of ionic compound ▪ Smallest whole-number ratio of ions 24 Formation of Ionic Compounds Metal + Non-metal  ionic compound 2Na(s) + Cl2(g)  2NaCl(s) Na + Cl Na+ + Cl NaCl(s) e 25 Cations Ionic Compounds ▪ Positively charged ions ▪ Formed from metals ▪ Atoms lose electrons e.g., Na has 11 e– and 11 p Anions Na+ has 10 e– and 11 p ▪ Negatively charged ions ▪ Formed from non-metals ▪ Atoms gain electrons e.g., Cl has 17 e– and 17 p Cl– has 18 e– and 17 p 26 Ions of Representative Elements ▪ Can use periodic table to predict ion charges ▪ When we use North American numbering of groups: Cation positive charge = group number 27 Ions of Representative Elements ▪ Noble gases are especially stable Nonmetals ▪ Negative (–) charge on anion = number of spaces you have to move to right to get to noble gas ▪ Expected charge on O N O F Ne ▪ Move two spaces to right ▪ O2– ▪ What is expected charge on N? ▪ Move three spaces to right ▪ N3 – 28 Rules For Writing Ionic Formulas 1. Cation given first in formula 2. Subscripts in formula must produce electrically neutral formula unit 3. Subscripts must be smallest whole numbers possible ▪ Divide by 2 if all subscripts are even ▪ May have to repeat several times 4. Charges on ions not included in finished formula unit of substance ▪ If no subscript, then 1 implied 29 Determining Ionic Formulas Example: Formula of ionic compound formed when magnesium reacts with oxygen ▪ Mg is group 2A ▪ Forms +2 ion or Mg2+ ▪ O is group 6A ▪ Forms –2 ion or O2– ▪ To get electrically neutral particle need ▪ 1:1 ratio of Mg2+ and O2– ▪ Formula: MgO 30 Determining Ionic Formulas “Criss-cross” rule ▪ Make magnitude of charge on one ion into subscript for other ▪ When doing this, make sure that subscripts are reduced to lowest whole number. Example: What is the formula of ionic compound formed between aluminum and oxygen ions? Al3+ O2– Al2O3 31 Your Turn! Which of the following is the correct formula for the formula unit composed of potassium and oxygen ions? A. KO B. KO2 C. K2O D. P2O3 E. K2O2 32 Your Turn! Which of the following is the correct formula for the formula unit composed of Fe3+ and sulfide ions? A. FeS B. Fe3S2 C. FeS3 D. Fe2S3 E. Fe4S6 33 Your Turn! Which of the following is the correct formula for the formula unit composed of ions of magnesium and nitrogen? A. MgN B. Mg3N2 C. Mn3N2 D. N3Mg2 E. Mn2N3 34 Cations of Transition Metals Transition metals ▪ Center (shorter) region of periodic table ▪ Much less reactive than group 1A and 2A ▪ Still transfer electrons to nonmetals to form ionic compounds ▪ number of electrons transferred less clear ▪ Form more than one positive ion ▪ Can form more than one compound with same non-metal e.g., Fe + Cl FeCl2 and FeCl3 35 Cations of Post-transition Metals Post-transition metals ▪ Nine metals Ga, In, Sn, Tl, Pb, Bi, Uut, Uuq, Uub ▪ After transition metals and before metalloids ▪ Two very important ones – tin (Sn) and lead (Pb) ▪ Both have two possible oxidation states ▪ Both form two compounds with same nonmetal e.g., Ionic compounds of tin and oxygen are ▪ SnO and SnO2 ▪ Bismuth ▪ Only has +3 charge ▪ Bi3+ 36 Ions of Some Transition Metals and Post-transition Metals 37 Compounds with Polyatomic Ions Binary compounds ▪ Compounds formed from two different elements Polyatomic ions ▪ Ions composed of two or more atoms linked by molecular bonds ▪ If ions are negative, they have too many electrons ▪ If ions are positive, they have too few electrons ▪ Formulas for ionic compounds containing polyatomic ions ▪ Follow same rules as ionic compounds ▪ Polyatomic ions are expressed in parentheses 38 Polyatomic Ions 39 Learning Check Ex. What is the formula of the ionic compound formed between ammonium and phosphate ions? ▪ Ammonium = NH4+ ▪ Phosphate = PO43– (NH4)+ (PO4)3– (NH4)3PO4 Ex. Between strontium ion and nitrate ion? ▪ Strontium = Sr2+ ▪ Nitrate = NO32– Sr2+ (NO3)– Sr(NO3)2 40 Nomenclature (Naming) ▪ IUPAC system to standardize name of chemical compounds ▪ One system so that anyone can reconstruct formula from name ▪ We will look at naming ionic compounds of ▪ Representative metals ▪ Transition metals ▪ Monatomic ions ▪ Polyatomic ions ▪ Hydrates 41 Naming Ionic Compounds Cations: ▪ Metal that forms only one positive ion ▪ Cation name = English name for metal ▪ Na+ sodium ▪ Ca2+ calcium ▪ Metal that forms more than one positive ion ▪ Use Stock System ▪ Cation name = English name followed by numerical value of charge written as Roman numeral in parentheses (no spaces) ▪ Transition metal ▪ Cr2+ chromium(II) Cr3+ chromium(III) 42 Naming Ionic Compounds Anions: ▪ Monatomic anions named by adding “–ide” suffix to stem name for element ▪ Polyatomic ions use names in Table 2.4 43 Learning Check: Name The Following ▪ K2O potassium oxide ▪ NH4ClO3 ammonium chlorate ▪ Mg(C2H3O2)2 magnesium acetate ▪ Cr2O3 chromium(III) oxide ▪ ZnBr2 zinc bromide 44 Learning Check: Determine The Formula ▪ Calcium hydroxide ▪ Ca(OH)2 ▪ Manganese(II) bromide ▪ MnBr2 ▪ Ammonium phosphate ▪ (NH4)3PO4 ▪ Mercury(I) nitride ▪ (Hg2)3N2 45 Your Turn! Which is the correct name for Cu2S? A. B. C. D. E. copper sulfide copper(II) sulfide copper(II) sulfate copper(I) sulfide copper(I) sulfite 46 Your Turn! Which is the correct formula for ammonium sulfite? A. NH4SO3 B. (NH4)2SO3 C. (NH4)2SO4 D. NH4S E. (NH4)2S 47 Hydrates ▪ Crystals that contain water molecules e.g., Plaster: CaSO4∙2H2O calcium sulfate dihydrate ▪ Water is not tightly held ▪ Dehydration ▪ Removal of water by heating ▪ Remaining solid is anhydrous (without water) Blue = White = CuSO4 CuSO4 •5H2O 48 Naming Hydrates ▪ Ionic compounds ▪ Crystals contain water molecules ▪ Fixed proportions relative to ionic substance ▪ Naming ▪ Name ionic compound ▪ Give number of water molecules in formula using Greek prefixes monoditritetrapenta- = = = = = 1 2 3 4 5 hexaheptaoctanonadeca- = = = = = 6 7 8 9 10 49 Learning Check: Naming Hydrates ▪ CaSO4·2H2O ▪ calcium sulfate dihydrate ▪ CoCl2·6H2O ▪ cobalt(II) chloride hexahydrate ▪ FeI3·3H2O ▪ iron(III) iodide trihydrate 50 Your Turn! What is the correct formula for copper(II) sulfate pentahydrate? A. CuSO4 · 6H2O B. CuSO3 · 5H2O C. CoSO4 · 4H2O D. CoSO3 · 5H2O E. CuSO4 · 5H2O 51 Your Turn! What is the correct name for Fe(NO3)3·9H2O A. iron nitrate nonahydrate B. iron(III) nitrate nonahydrate C. Ferium (III) nitrate decahydrate D. iron(III) nitrite nonahydrate E. iron(III) nitrate heptahydrate 52 Molecules vs. Ionic Compounds Molecules ▪ Discrete unit ▪ Water = two hydrogen atoms bonded to one oxygen atom Ionic Compounds ▪ Ions packed as close as possible to each other ▪ Sodium chloride: Six anions surround each cation; six cations surround each anion ▪ No one ion “belongs” to another 53 Molecular Compounds ▪ Formed when nonmetals combine ▪ C + O2  CO2 2H2 + O2  2H2O ▪ Millions of compounds can form from a few non-metals ▪ Organic chemistry and biochemistry ▪ Deal with chemistry of carbon + hydrogen, nitrogen, and oxygen ▪ A few compounds have only two atoms ▪ Diatomics: HCl, CO, HF, NO ▪ Most molecules are far more complex ▪ Sucrose (C12H22O11) urea (CON2H4) 54 Nomenclature of Molecular Compounds ▪ Goal is a name that translates clearly into molecular formula Naming Binary Molecular Compounds ▪ Which two elements present? ▪ How many of each? Format: ▪ First element in formula ▪ Use English name ▪ Second element ▪ Use stem and append suffix –ide ▪ Use Greek number prefixes to specify how many atoms of each element 55 Naming Binary Molecular Compounds 1. hydrogen chloride 1H 1 Cl HCl 2. phosphorous pentachloride 3. triselenium dinitride 1P 5Cl 3 Se 2N PCl5 Se3N2 ▪ Mono always omitted on first element ▪ Often omitted on second element unless more than one combination of same two elements e.g., Carbon monoxide CO Carbon dioxide CO2 ▪ When prefix ends in vowel similar to start of element name, drop prefix vowel 56 Learning Check: Name Each Format: ▪ Number prefix + first element name ▪ Number prefix + stem + –ide for second element ▪ AsF3 = arsenic trifluoride ▪ ▪ ▪ ▪ ▪ HBr N2O4 N2O5 CO CO2 = = = = = hydrogen bromide dinitrogen tetroxide dinitrogen pentoxide carbon monoxide carbon dioxide 57 Your Turn! Which is the correct formula for nitrogen triiodide? A. N3I B. NI3 C. NIO3 D. N(IO3)3 E. none of the above 58 Your Turn! Which is the correct name for P4O10? A. phosphorus oxide B. phosphorous decoxide C. tetraphosphorus decoxide D. tetraphosphorus oxide E. decoxygen tetraphosphide 59 Your Turn! Which is the correct formula for disulfur decafluoride? A. Su2F10 B. SF5 C. S2F10 D. S3F10 E. S2F4 60 Exceptions to Naming Binary Molecules Binary compounds of nonmetals + hydrogen ▪ No prefixes to be used ▪ Get number of hydrogens for each nonmetal from periodic table ▪ Hydrogen sulfide = H2S ▪ Hydrogen telluride = H2Te Molecules with Common Names ▪ Some molecules have names that predate IUPAC systematic names ▪ Water H 2O ▪ Sucrose C12H22O11 ▪ Ammonia NH3 ▪ Phosphine PH3 61 Summary of Naming 62

Elements, Compounds, and the Periodic Table

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