L-1 Atoms, Molecules and Ions - Copy PDF

‫بسم هللا الرحمن الرحيم‬ Faculty of Applied Health Sciences Technology Organic CHEMISTRY (AHS 111) Pharm D Student (1st level, 1st semester) (1) ‫ حجاج حسن‬/‫دكتور‬ Organic Chemistry AHS111 ‫بسم هل...

‫بسم هللا الرحمن الرحيم‬ Faculty of Applied Health Sciences Technology Organic CHEMISTRY (AHS 111) Pharm D Student (1st level, 1st semester) (1) ‫ حجاج حسن‬/‫دكتور‬ Organic Chemistry AHS111 ‫بسم هللا الرحمن الرحيم‬ Atoms, Molecules, and Ions Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten  “The Central Science” Astronomy Nuclear Chemistry Health and Medicine Biology Physics Chemistry Biology Geology Plant Sciences Biochemistry Environmental Science Dalton’s Postulates The Atomic Structure Rutherford postulated a very small, dense nucleus with the electrons around the outside of the atom. Most of the volume of the atom is empty space. Subatomic Particles Protons were discovered by Rutherford in 1919. Neutrons were discovered by James Chadwick in 1932. Protons and electrons are the only particles that have a charge. Protons and neutrons have essentially the same mass. The mass of an electron is so small we ignore it. Symbols of Elements Elements are symbolized by one or two letters. All atoms of the same element have the same number of protons: The atomic number (Z) The mass of an atom in atomic mass units (amu) is the total number of protons and neutrons in the atom. Isotopes: Atoms of the same element with different masses. Isotopes have different numbers of neutrons. 11 12 13 14 6 C 6 C 6 C 6 C Practice Questions Practice Exercise Determining the Number of Subatomic Particles in Atoms How many protons, neutrons, and electrons are in (a) a 138Ba atom, (b) an atom of phosphorus-31? Practice Questions Sample Exercise Writing Symbols for Atoms Give the complete chemical symbol for the atom that contains 82 protons, 82 electrons, and 126 neutrons. Average Mass Because in the real world we use large amounts of atoms and molecules, we use average masses in calculations. Average mass is calculated from the isotopes of an element weighted by their relative abundances. Periodic Table: A systematic catalog of elements. Elements are arranged in order of atomic number. Periodicity When one looks at the chemical properties of elements, one notices a repeating pattern of reactivities.  Periodic Table The rows on the periodic chart are periods. Columns are groups. Elements in the same group have similar chemical properties. Groups These five groups are known by their names. Periodic Table Nonmetals are on the right side of the periodic table (with the exception of H). Periodic Table Metalloids border the stair-step line (with the exception of Al and Po). Periodic Table Metals are on the left side of the chart. Practice Questions Sample Exercise Using the Periodic Table Which two of these elements would you expect to show the greatest similarity in chemical and physical properties: B, Ca, F, He, Mg, P? Exercise Locate Na (sodium) and Br (bromine) in the periodic table. Give the atomic number of each and classify each as metal, metalloid, or nonmetal.  Diatomic Molecules These seven elements occur naturally as molecules containing two atoms. Chemical Formulas The subscript to the right of the symbol of an element tells the number of atoms of that element in one molecule of the compound. Molecular compounds are composed of molecules and almost always contain only nonmetals. Types of Formulas Empirical formulas give the lowest whole-number ratio of atoms of each element in a compound. Molecular formulas give the exact number of atoms of each element in a compound. Molecular: C4H10 Empirical: C2H5 Types of Formulas Structural formulas show the order in which atoms are bonded. Perspective drawings also show the three-dimensional array of atoms in a compound.  Ions When atoms lose or gain electrons, they become ions (to have same # of e- as closest noble gas). Cations are positive and are formed by elements on the left side of the periodic chart. Anions are negative and are formed by elements on the right side of the periodic chart. Ionic Bonds Ionic compounds (such as NaCl) are generally formed between metals and nonmetals. Practice Questions Sample Exercise Writing Chemical Symbols for Ions Give the chemical symbol, including superscript indicating mass number, for the ion with 22 protons, 26 neutrons, and 19 electrons Practice How many protons, neutrons, and electrons does the 79Se2– ion possess? Practice Questions Sample Exercise Identifying Ionic and Molecular Compounds Which of these compounds are molecular: CBr4, FeS, P4O6, PbF2? Common Anions