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BMC seminar 1. Introduction to general chemistry The SI system of measurement. Elements. Symbols for the elements. Atoms. The structure of atoms. Nuclear arithmetic. Molecules and ions, compounds and mixtures Express the following numbers in scientific notation. Give the significant numbers in each case. Significant numbers 124556500000 = 1.245565 x 1011 7-12 0.0000005456 = 5.456 x 10-7 4 115 = 1.15 x 102 3 4568020 = 4.56802 x 106 6-7 0.0000789 = 7.89 x 10-5 3 0.01457 = 1.457 x 10-2 4 0.7890 = 7.890 x 10-1 4 The SI system of measurement. List the fundamental SI units of measure. What SI prefixes correspond to the following multipliers? 106 mega, M 10-12 pico, p 10-1 deci, d 10-6 micro, μ 101 deka, da Give the symbol and multipliers for the following prefixes. Symbol, factor • kilo k, 103 • nano n, 10-9 • milli m, 10-3 • centi c, 10-2 • femto f, 10-15 Mass Make each of the following conversions. 0.05 μg = ___mg = ___ ng 1 μg = 10-6 g 1 mg = 10-3 g 1 ng = 10-9 g 1 g = 103 mg 1 g = 109 ng 0.05 μg = 5x10-8 g 0.05 μg = 5x10-8 g = 5x10-8 x 103 mg = 5x10-5mg 0.05 μg = 5x10-8 g = 5x10-8 x 109 ng = 5x101ng = 50 ng Lenght Make each of the following conversions. 5 pm = ___cm = ___ nm 1 pm = 10-12 m 1 cm = 10-2 m 1 nm = 10-9 m 1 m = 102 cm 1 m = 109 nm 5 pm = 5x10-12 m 5 pm = 5x10-12 m =5x10-12 x102 cm = 5x10-10cm 5 pm = 5x10-12 m =5x10-12 x109 nm = 5x10-3nm Temperature Make each of the following conversions: 305 K to oC 305-273 = 32 oC 45 oC to K 45+273 = 318 K List some derived units. Make each of the following conversions: 1 dm3 = 1 L 1 dm3 = 1∙10-3 m3 1 cm3 = 1 mL 1 cm3 = 1∙10-3 L 1 cm3 = 1∙103 μL Make the following conversions: 67 cm3 = ___ m3 = ___ mm3 1 cm = 10-2 m = 101 mm 1 cm3 = 1 cmx1cmx1cm=10-2mx10-2m x10-2m =10-6m3 1 cm3 = 103 mm3 67 cm3 = 67x10-6 m3 = 6.7 x10-5 m3 67 cm3 = 67x103 mm3 = 6.7 x104 mm3 Volume Density What is the density of the element copper (in grams per cubic centimeter) if a sample weighing 324.5 g has a volume of 36.2 cm3? What is the mass in grams of a 19 cm3 piece of lead? The density of lead is 11.3 g/cm3. Mass = density x volume Mass = 11.3 g/cm3x 19 cm3 = 214.7 g Energy Definition: the capacity to supply heat or do work. Kinetic energy: the energy of motion. EK 1 2 mv 2 Potential energy: stored energy or energy of position m2 Unit of energy: 1J kg 2 s E p mgh Carry out the following conversions. • 3.5x 10-3 m to pm 3.5 x 109pm • -25C to K 248 K • 12 l to cm3 0.012 cm3 • 53 mg to kg 5.3 x 10-5 kg • 200 Pa to MPa 2 x 10-4 MPa • 0.5 hour to s 1800 s • 1.5 g/cm3 to kg/m3 1.5 x 103 kg/m3 Properties of matter Give the type (extensive/intensive; quantitative/qualitative) for the following physical properties: • • • • • • • • • • Volume Intensive Temperature • Temperature Color • Color Density • Density Mass • Boiling point Boiling point • Physical state Length Physical state • Independent of size Area Heat Extensive Mass Volume Heat Length Area Dependent of size Give the definition for physical and chemical properties. • Physical properties: characteristics of a material which may be determined without altering the composition of the material; boiling point, melting point, color, density etc. • Chemical properties: characteristics of a material which involves altering the composition of the material; the ability to form new substances by decomposition or reactions with other substances. Classify the following properties as physical or chemical property. A. color physical B. boiling point physical C. rusting chemical D. flammability chemical E. solubility physical Classification of matter Element • consists of only one kind of atom •cannot be broken down into any simpler type of matter by either physical or chemical means •can exist as either atoms (e.g. argon) or molecules (e.g., nitrogen). Compounds •consists of atoms of two or more different elements bound together •can be broken down into a simpler type of matter (elements) by chemical means (but not by physical means) •has properties that are different from its component elements •always contains the same ratio of its component atoms. Mixtures •consists of two or more different elements and/or compounds physically intermingled •can be separated into its components by physical means •often retains many of the properties of its components. Classify the following substances as element, compound or mixture. A. iron element B. ice compound C. concrete mixture D. tomato juice mixture E. table salt compound mixture of two elements an element a compound Chemical Symbols an abbreviation for the element one or two letters; the first Letter is ALWAYS capitalized. The second letter (if any) is lowercase. Give the chemical symbol for each of the following elements. A. Fluorine F B. Manganese Mn C. Sodium Na D. Cobalt Co E. Iron Fe Give the English name of the elements. A. C Carbon B. N Nitrogen C. S Sulphur D. Hg Mercury E. Ag Silver Where can you find the following groups in the perodic table? A. B. C. D. Alkali metals Noble gases Halogens Actinides Properties of metals and nonmetals Color: Malleability: Conductivity: Melting point: Metals Nonmetals •Silvery shine •Malleable •Good conductors of heat and electricity •Melt at high temperature •Brightly colored •brittle •poor conductor, good insulator •low melting point Semimetals •Silvery in apperance •Brittle •Poor conductors, semiconductors Identify the following elements as metals, nonmetals or semimetals. Mg metal Sr Br metal nonmetal Si semimetal Ag metal S nonmetal Atoms. The structure of atoms. Nuclear arithmetics. Elements are made of tiny particles called atoms. What is an atom? How is it put together? What are the parts of an atom? Atoms: the smallest component of an element which carries the chemical characteristics. Composed of a nucleus surrounded by electrons. An atom contains specific number of protons, neutrons, and electrons. Atomic Numbers and Mass Numbers Atomic number (Z) = number of protons in the nucleus. Mass number (A) = total number of protons and neutrons in the nucleus. Fill in the following table for each of the species below: 12 6 C 19 9 F 24 2 12 Mg A Z N Number of electrons 12 6 6 6 0 Symbol Electrical charge 19 9 10 9 0 24 12 12 10 +2 Give the symbol of the element with the mass number 39 and 20 neutron. A=Z+N Z = A – N = 39-20 = 19 →K Isotopes Isotopes have the same Z but different A. Chlorine has two main isotopes, with neutron numbers 18 and 20. Look up the atomic number of chlorine, tell how many neutrons each isotope contains, and give the standard symbol for each. 35 17 Cl 37 17 Cl Atomic mass Atomic mass unit or Dalton Protons and neutrons each have a mass of almost exactly 1 amu. The mass of an atom in amu ≈ the atom's mass number. Atomic mass of an element 35Cl isotope has a mass of 35 amu and is 75.8% abundant. 37Cl isotope has a mass of 37 amu and is 24.2% abundant. Average atomic mass = (Fraction abundance of isotope 1) x (mass of isotope 1) + (Fraction abundance of isotope 2) x (mass of isotope 2) Average atomic mass of Cl = (0.758)(35 amu) + (0.242)(37 amu) = 35.45 amu Copper metal has two naturally occuring isotopes: copper-63 (69.17%; isotopic mass = 62.94 amu) and copper-65 (30.83%; isotopic mass = 64.93 amu). Calculate the atomic mass of copper and check the answer in the periodic table. 63 29 Cu 65 29 Cu isotope has a mass of 62.94 amu and is 69.17% abundant. isotope has a mass of 64.93 amu and is 30.83% abundant. Average atomic mass of Cu = (0.6917)(62.94 amu) + (0.3083)(64.93 amu) = 63.55 amu Molecules – Distinct packages of atoms bound together by sharing electrons (covalent bonds) – can be same element or different elements (O2, HCl,C12H22O11,...) – must be neutral (no charge) – nonmetal with nonmetal • Diatomic elements Ions - form by tranfer of electrons - ionic bond generally forms between a nonmetal and a metal - ionic solid: cations and anions are packed together in a regular way Cl + e- Cl- Na+ Cl- Na Na+ + e- Which of the following compounds would you expect to be ionic and which molecular? A. B. C. D. E. F. G. H. CH4 water CaF2 BrCl KCl H2S CH3CH2OH NaOH molecular molecular ionic molecular ionic molecular molecular ionic Which of the following drawings is most likely to represent an ionic compound, and which a molecular compound? ionic molecular