University:
Glendale Community College
Course:
CHM130 | Fundamental Chemistry
Academic year:

2019
Views:

357

Pages:

2
Author:

kekoman79

Name: ___KEY______________________ Section: _____________ Chapter 2 Worksheet: Atoms, Molecules, and Ions 1. Briefly define the following: a. Law of Conservation of Mass Matter is neither created nor destroyed in a chemical reaction – molecules change to create new substances. b. Law of Definite Proportions All samples of a given substance will have the same ratio of atoms by mass (e.g., carbon dioxide is always CO2). c. Dalton’s Atomic Theory 4 postulates: all matter is made of atoms (once thought to be indivisible); all atoms of a given elements are identical (atoms of different elements are different); atoms are not created or destroyed in a reaction; atoms combine in small, whole-number ratios to form compounds. d. Law of Multiple Proportions Two different compounds made up of the same elements will have mass ratios that are small whole-number ratios of each other. For example, ratio of oxygen in CO to oxygen in CO2 is 1:2. 2. Describe the contribution made by the following scientists: a. Priestley Isolated oxygen by heating HgO in a closed container to observe conservation of mass. b. Lavoisier Discovered Law of Definite Proportions. c. Thomson Worked with cathode ray tubes to discover the presence of electrons in the atom. d. Millikan Used the oil drop experiment to calculate the charge (in Coulombs) of an electron. e. Rutherford Used the gold foil experiment to determine the structure of an atom (relative positions of protons and electrons). 3. Fill in the table below: Symbol Atomic Number 1 Mass Number Number of Neutrons 1 1 0 O 8 17 9 Hg 80 199 119 Cu 29 63 34 35 71 36 1H 17 199 63 71 Br page 1 Name: ___KEY______________________ Section: _____________ 4. How many gold-197 atoms are in a 0.156 gram sample? (Watch sig figs in your answer!) 4.77 x 1020 atoms 5. Classify the following as a mixture or pure substance, and atom, molecule, or compound. a b c d Pure substance; Molecules Mixture of atoms and compounds Pure substance; compound Pure substance; Atoms e f g h Mixture of atoms and molecules Mixture of atoms and molecules Mixture of molecules Mixture of atoms i j k l Mixture of compounds Pure substance; Atoms Mixture of atoms and molecules Pure substance; Molecules 6. Describe the difference between ionic and covalent compounds. Ionic bonds form when electrons transfer from one atom to another (between metals and nonmetals). Covalent bonds form when electrons are shared between atoms (between two or more nonmetals). 7. Circle the substances that are ionic in the list below: CH4 LiCl C2H4 NaNO3 CoCl2 CO2 KBr page 2