The Chemical view of matter • Element • Chemical compounds-atoms in combination • Mixtures and pure substances • Changes in matter is it physical or chemical • Classification of matter 1 Classification of matter 2 Mixtures • Heterogeneous mixtures • Homogeneous mixtures 3 Basic definition • A pure substance is something with a uniform and fixed composition at the nanoscopic level. • An element is a pure substance composed of only kind of atom • An atom is the smallest particle of an element, the atoms of different elements are different. 4 Chemical compound-atoms in combination • Chemical compound are pure substances (Molecule) made of atoms of different elements combined in definite ways (fix ratio). • Molecule is the smallest chemical unit of a compound that retain the composition and properties of the compound and exist independently 5 The atomic symbol A Z X X = element symbol Mass number, A = number of protons + neutron in nuclease = Z + N Atomic number, Z = number of protons Neutral atom Z =number of electron 6 the periodic table entry for copper 29 Atomic number Cu symbol 63.546 Atomic weight 7 8 9 The Element http://www.elmhurst.edu/~chm/vchembook/102Aelement.html10 Compound and Molecule • Molecule is the smallest chemical unit of a compound that retain the composition and properties of the compound and exist independently – Mononuclear molecule – Heteronuclear molecule 11 Using chemical symbol • Chemical formula: Written combination of element symbols that represent the atom combined in a chemical compound Ex. Table sugar sucrose C6H12O6 12 Using chemical symbol • Structural formula H H H H H N H H C H O C O H CO H NH 2 2 3 Carbon dioxide molecule Hydrogen molecule Ammonia molecule CH4 Methane molecule 13 Seven nonmetals exist under everyday condition as two-atom molecule (diatomic molecule) 14 15 • Why does an element or compound have the properties it has? • Why does one element or compound undergo a change that another element or compound will not undergo? 16 Modern view of atom 17 Where are the electron in atoms • Bohr’s model of the atom 18 Bohr’s model of the atom 19 Quantum mechanic for atomic structure Electron location are defined in term of regions of probability known as orbital Principle shell Subshell = defferent energy in given subshell orbital 20 Quantum mechanic for atomic structure 21 Electron Configurations and the Periodic Table Group IA Group VIIA H 1s1 Li [He] 2s1 F [He] 2s2 2p5 Na [Ne] 3s1 Cl [Ne] 3s2 3p5 K [Ar] 4s1 Br [Ar] 4s2 3d10 4p5 Rb [Kr] 5s1 I [Kr] 5s2 4d10 5p5 Cs [Xe] 6s1 At [Xe] 6s2 4f14 5d10 6p5 22 23 Atomic Properties Li Na K 24 25 IUPAC recommend names for groups of elements in the periodic table Group number recommend names 1 Alkali metals 2 Alkali earth metals 15 Pnicogens 16 Chalcogens 17 Halogens 18 Noble gases 26 Isotope Isotopes are atom of the same elements with different mass numbers. Ex. 27 Electronegativity values Chemical bond and Electronegativity A------------B A---------A Nonpolar covalent polar covalent bond bond : equal sharing : unequal sharing of of a bond pair a bond pair polar covalent bond : equal EN(A)<EN(B) Ionicsharing bond : transferof a bond of an electronpair EN(A)<<EN(B) 29 Ionic bond and ionic compound Some commercially important ionic compounds with polyatomic ions Formula Name(common name) Uses NH4NO3 Ammonium nitrate fertilizes and explosive KNO3 Potassium nitrate Gunpowder and Match NaOH Sodium hydroxide preparing soap Mg(OH)2 magnesium hydroxide Milk of magnesia Na2CO3 Sodium carbonate water softening, detergent Some commercially important ionic compounds with polyatomic ions Formula Name(common name) Uses NaHCO3 sodium bicarbonate household use, (baking soda) fire extinguishers Na2PO4 sodium phosphate food additive Colvalent Molecule : structure explain chemical and physical properties Nonpolar covalent polar covalent bond bond : equal sharing : unequal sharing of of a bond pair a bond pair polar covalent bond : equal sharing of a bond pair Shape of molecules http://www.4college.co.uk/as/el/shapes.php Structure of ice http://www.files.chem.vt.edu/confchem/2004/b/sinex-gage/sinex- gage.html http://www.classzone.com/books/earth_science/terc/content/inve stigations/es0506/es0506page01.cfm 35 Name for binary molecular compound Ex. N2O4 dinitro tetraoxide CCl4 carbon tetrachloride Intermolecular force Intermolecular force Hydrogen Bonding Physical vs. Chemical Changes Physical changes occur when substances or objects undergo a change without changing into another substance Chemical changes are changes substances undergo when they become new or different substances. 42 Physical vs. Chemical Changes 43 Chemical change Chemical reaction A process in which one or more substance (the reactant) are convert to one or more different substance (the product) The reactant The product Ex. H O H2 + 1/2O2 2 water 44 Chemical equation • Representation of chemical reaction by formulas of reactant and product • To present correctly, chemical equation must be balanced the total number of atoms of each kind the same in reactant and product Ex. 2C (s) + O2 (g) 2CO2 (g) 45 The state of matter http://www2.gi.alaska.edu/alison/SNW_15_Matter.html Gas • ความหนาแน่นต ่ากว่าของแข็งและของเหลวมาก • ฟุ้งกระจาย มีการเคลื อนที ของอนุภาคตลอดเวลาอย่างไม่มีระเบียบ • โปร่งแสง • สมบัติขึ้นอยู่กับอุณหภูมิและความดัน • แก็สที อยู่ในภาชนะเดียวกันจะผสมกันได้อย่างสมบูรณ์และสม ่าเสมอ Formula Name Characteristics Gas H2 Hydrogen Flammable, lighter than air He Helium Colorless, nonflammable, lighter than air HCN Hydrogen cyanide Toxic, has been used historically to shorten people's lives HCl Hydrogen chloride Toxic, corrosive H2S Hydrogen sulfide Toxic, smells like rotten eggs CO Carbon monoxide Toxic, Jack Kervorkian's favorite gas CO2 Carbon dioxide Colorless, odorless, not toxic, but unsupportive of respiration CH4 Methane Colorless, odorless, flammable, occasional byproduct of the digestive system N2O Nitrous oxide Colorless, sweet odor, makes you feel "funny" NO2 Nitrogen dioxide Toxic, red-brown, irritating odor NH3 Ammonia Colorless, pungent odor SO2 Sulfur dioxide Colorless, irritating odor The Air we Breathe Liquid • มีปริมาตรคงที • ไหลได้และรูปร่างไม่แน่นอน • มีการเคลื อนอย่างไม่เป็นระเบียบ • มีแรงยึดเหนี ยวระหว่างโมเลกุล • ความดันมีผลต่อการเปลี ยนแปลงปริมาตรไม่มาก The Unique properties of water http://www.science.uwaterloo.ca/~cchieh/cact/applychem/waterchem.h tml The Unique properties of water The Unique properties of water •Water is a liquid at room temperature • The density of a solid water (ice) is less than that of liquid water • Water has a relative high heat capacity • Water has a high heat of vaporization • Water has the highest surface tension of all liquids except mercury • Water is excellent solvent, often referred to as the universal solvent • Water has a pH of 7 and can act as an acid or a base. • Water is the only substance on Earth that exists as a solid, liquid, and a gas. surface tension Adhesive forces Cohesive forces pollution water Clean water Water pollutant from industrial waste Household waste that affect water quality solid NaCl ice (H2O) Graphite and diamond http://www.popgive.com/2008/12/amazing-snowflake-and-snow-crystal.html Gold (Au) http://www.oknation.net/blog/snowy/2010/12/22/entry-1 http://www.pa.msu.edu/cmp/uec/News.htm .