Formation of Compounds

Formation of CompoundsCh. 4

Forming CompoundsValence electrons:Out most electronsIons:-Cations; positively charged by losing electrons; Na+-Anions; negatively charged by gaining electrons; Cl-Octet Rule:Atoms are most stable when they have 8 valence electronsIsoelectronic:Having the same number of valence electrons

K+ = Ar F = Cl Xe = Ba2+

Compounds and their PropertiesCompounds have very different properties than the elements that the are made of

SubstanceTemperatureStability ColorStateTraitNaCl800oC (melts)Stable crystal WhiteSolid compoundImportant to living thingsNa98oC (melts)Violently reactive Silver-whiteSoft solidNot found naturallyCl-34oC (condenses)Very reactivePale greenGasPoisonous

How Compounds FormOctet ruleElements was to achieve a Noble Gas configurationTransition metals have a Pseudo-Noble Gas configurationHave a filled outer level (s-level) but space in d-level allows for bonding to occurBonding types:Ionic: Electron taking bondsCovalent: Electron sharing bonds

Ionic CompoundsBond between cations and anionsCation are always metalsAnion are always non-metalsCompound should have a net charge of 0Anion takes the electron because it is always more electronegative than the cationNaming:First element- regular element nameSecond element- replace ending with ideNaCl- Sodium + Chlorine = Sodium chlorideKI-BaCl2- Al2O3-

Potassium iodideBarium chloride Aluminum Oxide

Ionic Compound StructureIonic compounds form crystal latticeMakes compound brittle and hard

Ionic compounds dissolve and H2O and become free floating ionsElectrolytesCompound that helps electricity flow through water

Ionic Compound Lewis Dot StructureWhen drawing ions set to form a compound use different colors or dot styles for each elementWhen drawing the ionic compound:The cation has no dotsThe anion must have a full shell (8 dots)Net charge of the compound is 0

Ionic Compound Lewis Dot StructureAl3+ + Cl- ?

Covalent CompoundsElectron sharing between non-metals; use the term moleculeWeaker than ionic bondsCan form multiple bonds between multiple pairs of electrons1 pair is a single bond (weakest)2 pair is a double bond 3 pair is a triple bond (strongest)Bonding occurs to achieve Noble Gas configuration

Covalent Compound Lewis Dot StructureDraw ions using normal dot structure rulesDraw the molecule with bond lines replacing the shared electrons

Covalent Compound NamingNaming rules differ from ionic compoundsFirst element uses the normal element nameSecond element uses ide ending ruleNumber of each element must be stated

CO2- N2O4- H2O-

12345MonoDiTriTetraPenta678910HexaHeptaOctaNonaDecaCarbondioxideDinitrogentetraoxideDihydrogenoxide

Covalent vs. Ionic CompoundsInterparticle ForcesForces between particles of a substanceIonic compounds have very strong interparticles forces due to + and charges from the ions-commonly found as solidsCovalent compounds have no charge so their interparticles are very weak-commonly found as liquids and gases-solid covalent compounds melt at low temps.-many do not dissolve in water