Chem 101 - General Chemistry (Inorganic Section) PDF

General Chemistry Chem 101 (Inorganic Section) Prof. Dr. Ayman Ayoub Abdel-Shafi Professor of Inorganic Chemistry [email protected] FB/@ASCAyoub Chemistry  Chemistry is the study of matter and the changes it undergoes.  Ch...

General Chemistry Chem 101 (Inorganic Section) Prof. Dr. Ayman Ayoub Abdel-Shafi Professor of Inorganic Chemistry [email protected] FB/@ASCAyoub Chemistry  Chemistry is the study of matter and the changes it undergoes.  Chemistry is often called the central science, because a basic knowledge of chemistry is essential for the study of biology, physics, geology, ecology, and many other subjects. Chemistry  We all do chemistry every day! As soon as you wake up in the morning, you start doing chemistry.  Chemistry explains why an egg changes when you fry it and why your non-stick pan is non-sticky.  Chemistry explains how soap and shampoo make you clean, why you feel tired before coffee and alert after it, and how the petrol in your car gets you to work. Dalton’s Atomic Theory (~1803) ▪ All matter is made of tiny, indivisible particles called atoms. ▪ Atoms of the same element are identical. ▪ Atoms of different elements combine in whole number ratios to form compounds. ▪ Chemical reactions involve the rearrangement of atoms. J. J. Thomson (1856-1940) Noble prize 1906 in physics The Electron  In 1897, the British physicist J. J. Thomson (1856–1940) proved that atoms were not the ultimate form of matter.  He demonstrated that cathode rays could be deflected, or bent, by magnetic or electric fields, which indicated that cathode rays consist of charged particles. CRT experiment http://www.youtube.com/wat ch?v=GzMh4q-2HjM Because the cathode ray is attracted by the plate bearing positive charges and repelled by the plate bearing negative charges, it must consist of negatively charged particles “electrons”.  J. J. Thomson, used a cathode ray tube and his knowledge of electromagnetic theory to determine the ratio of electric charge to the mass of an individual electron  The number he came up with was -1.76 × 108 C/g, where C stands for coulomb, which is the unit of electric charge. Robert Millikan, (1868-1953) Noble prize 1923 in physics Charge of the electron  Millikan (1917) succeeded in measuring the charge of the electron with great precision  Millikan found that the charge of an electron to be -1.6022 × 10-19 C. Mass of the electron  From these data he calculated the mass of an electron:  Mass of the electron= 9.1 x 10-28 g By the early 1900s Radioactivity  Near the turn of the 20th century, French scientists discovered radioactivity, the emission of particles and/or radiation from atoms of certain elements E. Rutherford (1871-1937) Noble prize 1908 in chemistry Rutherford—Discovery of Nucleus (~ 1911)  Student of Thomson’s—believed in the plum pudding model of the atom. Thomson and Rutherford  Fluorescent Lead Radium Screen block Gold Foil When the alpha particles hit the fluorescent screen, the screen would glow.  What he expected… The alpha particles should pass through without changing direction very much. According to Rutherford:  Most of the atom must be empty space  The atom’s positive charges are all concentrated in the nucleus, which is a dense central core within the atom.  The positively charged particles in the nucleus are called protons.  Each proton carries the same quantity of charge as an electron.  mp = 1840 me  The nucleus occupies only about 1/1013 of the volume of the atom. A typical atomic radius is about 100 pm, whereas the radius of an atomic nucleus is only about 0.005 pm (pm = 10-12 m).  According to Rutherford, Hydrogen has 1 proton and He has 2 protons  Therefore; the mass of He = 2 H  Actually the mass of He is 4 times the mass of H.  Later experiments showed that there are more particles inside the nucleus with mass slightly larger than that of the protons “neutrons”. 2 Atomic Number, Mass Number and Isotopes Atomic Number (Z)  is the number of protons in the nucleus of each atom of an element.  In neutral atoms Z = no of protons = no of electrons The chemical identity of an atom can be determined from it atomic number. Mass Number (A)  isthe total number of protons and neutrons in the nucleus of each atom of an element.  Mass number = atomic number + number of neutrons A = Z + no of neutrons Mass number A Z X Element abbreviation Atomic number Isotopes  Atoms that have the same atomic number but different mass numbers. 1 H 2 H 3 H 1 1 1 Hydrogen Deuterium Tritium 3 Molecules and Ions Molecules  A molecule is an aggregation of at least two atoms held together by chemical bond. H2 diatomic molecule (not a compound) HCl molecule (compound) H2O polyatomic molecule (compound) Ions  An ion is an atom or a group of atoms that has a net positive or negative charge. The loss of one or more electrons from a neutral atom results in a cation. Na → Na+ + e The gain of one or more electrons from a neutral atom results in an anion. Cl + e → Cl- 1 2 Li+ O2- F- 3 Na+ Mg2+ S2- Cl- 4 K+ Ca2+ Br- 5 I- 6 7 4 Chemical Formulas Molecular Formulas  A molecular formula shows the exact number of atoms of each element in the smallest unit of a substance. H2 hydrogen HCl hydrochloric acid H2O water Structural Formulas  The structural formula shows how atoms are bonded to one another in a molecule. e.g., H-O-H Emperical Formulas  The emperical formula tells us which elements are present and the simplest whole number ratio of their atoms. e.g., H2O2 The emperical formula is HO Molecular formula H2 H2O NH3 CH4 Structural formula H H H H O H H N H H C H H H Emperical formula H2 H2O NH3 CH4 Formula of Ionic Compounds K + Br- KBr Zn2+ I- ZnI2 Al3+ O 2- Al2O3 5 Naming Compounds Ionic Compounds Ionic compounds are binary compounds or compounds formed from two elements Cation Anion CA Cation takes the name as the element Anion is named by taking the first part of the element name (chlorine) and adding “ide” Anionic groups OH- hydroxide CN- cyanide Anions CO32- carbonate HCO3- bicarbonate SO32- sulfite S2- sulfide NO2- nitrite S2O32- thiosulfate Anions Cl- chloride Br- bromide I- iodide NO3- nitrate SO42- sulfate PO43- phosphate Anions MnO4- permanganate CrO42- chromate Cr2O72- dichromate ClO3- chlorate Cations Fe2+ ferrous & Fe3+ ferric FeCl2 ferrous chloride & FeCl3 ferric chloride It does not tell the actual number of +ve charges Stock’s System Roman numbers are added to indicate the number of +ve charges Mn2+ : MnO manganese (II) oxide Mn3+ : Mn2O3 manganese (III) oxide Mn4+ : MnO2 manganese (IV) oxide Molecular Compounds HCl hydrogen chloride CO carbon monoxide & CO2 carbon dioxide SO2 sulfur dioxide & SO3 sulfur trioxide NO2 nitrogen dioxide & N2O4 dinitrogen tetroxide PCl3 phosphorous trichloride Acids and Bases Acid: is the substance that yields hydrogen ions (H+) when dissolved in water. Examples  HCl hydrochloric acid  HBr hydrobromic acid Oxoacids: are acids that contain hydrogen, oxygen and another element (the central element) HNO3 nitric acid H2CO3 carbonic acid H2SO4 sulfuric acid HClO3 chloric acid  “Per” acids Addition of one “O” to the “ic” acids HClO3 chloric acid HClO4 perchloric acid  “ous” acids Removal of one “O” from the “ic” acids HNO3 nitric acid HNO2 nitrous acid  Hypo…..ous acid Removal of two “O” from the “ic” acids HNO3 nitric acid HNO hyponitrous acid Base: is the substance that yields hydroxide ions (OH-) when dissolved in water. Examples  NaOH sodium hydroxide  Ba(OH)2 barium hydroxide