Chemical Bonding

metal (+) and nonmetal (-) , ionic

  • only ever single bonds

nonmetal (-) and nonmetal (-) , covalent

  • share electrons to obtain a stable noble gas configuration

  • single, double, or triple bonds

metal (+) and metal (+) , metallic

  • metals have more valence electron shell orbitals than electrons

  • delocalized electrons is what gives metals their characteristic properties, for example, if the ends of a bar of metal are connnected to a source of electric current, electrons from the external source enter the bar at one end

  • a bonding scheme for metals must also account for the properties metals share:

    1. conduct electricity

    2. conduct heat

    3. mallebility and ductility

    4. lustrous

  • they follow the electron sea model or the free electron model, where they have released their electrons and are embedded in a sea of electrons

octect rule - atoms react by sharing or transferring electrons in order to obtain a stable noble gas configuration. Noble gases (except He) have 8 valence electrons

metals lose electrons and form positive ions called cations

nonmetals gain electrons and from negative ions called anions

properties of ionic compounds:

  • crystalline solids at room temperature

  • arranged in a lattice strcture

  • high melting and boiling points, soluble, hard but brittle, conduct electricity when molten or aqueous

properties of of covalent compounds:

  • gases liquid and solid and room tempertature

  • solid are usually soft

  • evapourate readily and have low melting and boiling points

  • not soluble in polar, soluble in non polar

  • do not conduct electricity