Presentation on theme: "Chemical Bonding Chemical bond – The attractive force between the protons of one atom for the electrons of another atom Determined by electronegativity."— Presentation transcript:
1 Chemical BondingChemical bond – The attractive force between the protons of one atom for the electrons of another atomDetermined by electronegativityChemical energy – a type of stored (potential) energy that is involved in the formation and breaking of chemical bonds.When bonds break... energy is absorbed!CuSO4·5H2O + energy → CuSO H2O↑breaking this bond by adding energy!
2 Bonding When bonds form... energy is released! Mg + O → MgO + Energy Bonding & EnergyWhen bonds form, energy is released. Systems are more stable when they are at lower energy levels.Therefore, atoms become morestable when they form bondsdue to the release of energy.
3 Bonding Why do atoms bond? What group of elements do not bond? to become more stableto fill their valence shell(highest principal energy level)It takes eight electrons to fill the valence shell, except for elements that only need two.What group of elements do not bond?Noble Gasestheir outer shell is already completely filled.The Octet Rule- Atoms bond in order to have eight electrons in their valence shells(or sometimes two), giving them the same electronic configuration as a noble gas.Noble gases are stable. All elements want to be like the noble gases.
4 BondingIonic Bond – the bond that forms between metal and nonmetal. Electrons are transferred from the metal to the non-metal.The bond between cation and anion is very strong.Determines physical and chemical properties of ionic substancesIonic SubstancesCalled "Salts"solids form a crystalline shape called a “lattice”High melting points (solid at room temp.)brittlesolubility – ability to be dissolved.Ionic compounds dissolve in wateraqueous – dissolved in waterSalts do not conduct electricity as solidsDo conduct when melted(liquid) or aqueouselectricity is a flow of charged particlesIons(charged atoms) move freely when liquid or aqueous
5 Ionic Compounds - Oxidation state : the charge of the ion. Metals lose electrons and become positiveNonmetals gain electrons and become negativeThe number of electrons lost or gained determines oxidation stateEx: Ca is in Group 2, has 2 valence electronsbecomes Ca2+Therefore, its oxidation state = 2+Ex: N is in Group 15, has 5 valence electronsbecomes N3-Oxidation state = 3-Several metals have more than one oxidation stateMany are transition metalsExample:Copper can have one valence electron:Copper can also have 2 valence electrons:Cu+Cu2+
6 Xe Lewis-Dot Diagrams Lewis-Dot diagrams aka electron-dot diagrams or Lewis-Dot StructuresShows valence electrons for atomsMaximum number of valence electrons = 8 (think Octet Rule)Valence electrons are drawn around the outside of the element symbolThe first 4 electrons are filled one to each side(top, right, bottom, left)The next 4 electrons pair up with the first 4 after thatExample: Xenon is a noble gas, it has 8 valence electrons.Xe
7 Lewis-Dot Diagrams & Bonding Can assist in determining how elements bondMetals lose electronsNonmetals gain electronsDot diagrams show where and how many electrons are being transferred1. Determine the number of valence electrons for each element and draw them in2. Transfer electrons from the metal to the nonmetal3. Determine if more than one ion is needed to fill the valence shell4. Write the metal first with its oxidation state5. Write the non-metal second with a full outer shell and brackets6. Add coefficients if more than one atom was usedONaNa2Na+[ O ]2-
8 Chemical FormulasChemical formula- expression indicating the elements in the compound and how many in the smallest unit of a substance“Which atoms & how many”Subscripts indicate how many but 1s are not writtenEx. NaCl Ex. Fe2O3 Oxidation states can be determined from formulasChemical formulas are neutralAnion & cation charges must total to 0Start with the ion you know for sureExample: NaCl Na is Group 1 & always forms a 1+ ion. Therefore, Cl must be 1- to balance it.Example: Fe2O3· Fe is a transition metal, oxidation state is unknown· O is Group 16 & always forms 2- ion, and there are 3· Fe must be a 3+ in order to balance the negative charges of Oone Na atom and one Cl atomtwo Fe atoms and three O atoms
9 IUPAC Naming SystemBinary Compound – two different elements chemically combinedTwo parts: Cation (metal) & Anion (nonmetal)Ternary compounds – compounds with more than two elements.Polyatomic ion replaces an anion(or cation)Polyatomic ions – ions made from more than one elementOften made from multiple nonmetalsMost end in “-ate” or “-ite”List on Page 7 of NC Reference TablesIUPAC - International Union of Pure and Applied ChemistsThese guys made the naming systemCation is written first. Ending does not changeAnion is written second.If it’s a nonmetal, ending is changed to “-ide”If a polyatomic ion, ending is not changedCertain Transition metals need a roman numeral“Ti through Cu, Au, Hg, Sn & Pb”Examples:Sodium & chlorineCalcium & OxygenMagnesium and sulfateIron (II) and bromineSodium chlorideCalcium oxideMagnesium sulfateIron (II) bromide
10 Chemical Naming & Chemical Formulas Determining a name from a formulaSame rules for naming; Cation first, anion second, roman numerals for transition metalsThe amount indicated by subscripts doesn’t factor into the chemical name for ionic compoundsExample: MgBr2Li2SO4CuODetermine a formula from a chemical nameWrite the symbols for the cation & anionLook up the charges. Roman numerals indicate the charge on transition metalCalculate the amount of each ion and fill in subscriptsMagnesium bromideLithium sulfateCopper (II) oxide
11 Metallic Bonds Positive metal ions surrounded by valence electrons Valence electrons are held loosely, flow freely between ions“positive ions in a sea of mobile electrons”The bond is a result of the attraction between the positive ions and the mobile electrons.The delocalized valence electrons give metals their propertiesLuster, Malleability, Ductility, ability to conduct heat and electricity in the solid state.