大学化学课件CHAPTER3【荐】.pdf

Chapter 3: Molecules, compounds and chemical reactions Text sections 3.1 – 3.10 Key Concepts Types of Chemical Compounds Formulas, Formula Mass and Moles Chemical and % Composition Oxidation States Naming Inorganic Compounds Types of Compounds There are two main types of compounds : 1) Molecular Compounds - composed of molecules - usually contain non-metals - held together with covalent bonds (e- s shared between atoms - more later) - eg. carbon dioxide - CO2 2) Ionic Compounds - combination of a metal and a non-metal - made up of +’ve and -’ve ions - held together with electrostatic forces - eg. sodium chloride - NaCl Molecular Compounds and their Formulas Chemical Formula – representation of elements present and the relative # of atoms of each element. ex. elements present CCl No subscript 4 means 1 4 Cl atoms per unit atom per unit Three kinds of chemical formulas 1)Empirical Formula Provide increasing 2) Molecular Formula amounts of 3)Structural Formula information Empirical Formulas – simplest formula for a compound; gives types of atoms present and their relative #s. Subscripts always reduced to simplest whole number ratio. Molecular Formulas – based on an actual molecules. Subscripts not always reduced to their simplest whole number ratio Empirical and molecular formulas give no info on how atoms are attached to each other. Structural Formulas – shows order in which atoms are bonded in a molecule and what types of bonds. There are different types of structural formulas (see below).