Slides by Montgomery College licensed under CC BY 4.0.CHEMISTRY: ATOMS FIRSTCompounds: Ionic, Molecular, and Acidsand Composition of Compounds
IONIC & MOLECULAR COMPOUNDSAND COMPOSITIONThis unit is a mixture of several chapters.Thespecific chapters and sections covered in this set ofslides are listed below:3.7Molecular and Ionic Compounds4.3Chemical Nomenclature6.1Formula Mass and the Mole Concept (Review)6.2Determining Empirical and Molecular Formula2
3.7MOLECULAR AND IONIC COMPOUNDS3In an ordinary chemical reaction:•thenucleusof each atom remainsunchanged.•electrons can be shared between atoms to form chemical bonds.•atoms can gain or lose electrons resulting in electrically chargedparticles calledions.The Elements in Chemical Reactions
3.7MOLECULAR AND IONIC COMPOUNDS4Predicting Ion Formation•Theoctet rulestates that atoms will gain, lose or share electrons toachieve an octet of 8 valence electrons.•Main group atoms lose or gain electrons so that the overall electroncount is the same as the nearest noble gas (8 ve-).•Na atoms lose one electron and become Na+.•Na+has the same overall electron count asNe.•Na+has a positive charge and is acation.•Cl atoms gain one electron and become Cl-.•Cl-has the same overall electron count asAr.•Cl-has a negative charge and is ananion.•Transition metals have variable charges and are difficult to predict,but several only form one ion that you need to know:•Zn2+, Cd2+, and Ag+
alkalimetals1+alkalineearths2+halogens1-chalcogens2-transition metalsare variable3.7MOLECULAR AND IONIC COMPOUNDS5pnictogens3-Predicting Ion Formation•For main group elements, use the groups on the periodic table.
3.7MOLECULAR AND IONIC COMPOUNDS6Predicting Ion Formation•Practice prediction ion formation by filling in the table.AtomIonCation orAnion?NearestNoble GasMgKFOSrPSeCs
3.7MOLECULAR AND IONIC COMPOUNDS7Polyatomic Ions•Thus far, only monatomic ions have been discussed.•Groups of atoms bonded together into electrically chargedmolecules are known aspolyatomic ions.•These ions are very important and appear repeatedly in generalchemistry, organic chemistry, and biology.•The polyatomic ions are listed in Table 3.4 but many are listedbelowNH4+CN⎯CH3COO⎯CO32⎯HCO3⎯ClO⎯ClO2⎯ClO3⎯ClO4⎯NO2⎯NO3⎯PO43⎯HPO42⎯H2PO4⎯OH⎯SO32⎯SO42⎯HSO4⎯CrO42⎯Cr2O72⎯MnO4⎯
3.7MOLECULAR AND IONIC COMPOUNDS8Polyatomic Ions and Related Acids•Many important acids used in chemistry are related topolyatomic ions.
3.7MOLECULAR AND IONIC COMPOUNDS9Ionic Bonds•Electrons can betransferredfrom one atom to another.•Ionic bonds are formed by the electrostatic forces betweenanions and cations.Covalent Bonds•Alternatively, electrons can besharedbetween two atoms.•Covalent bonds are formed when one or more pairs of electronsare shared between two atomic nuclei.