Presentation on theme: "Comparison of Properties Ionic Compounds Covalent Compounds Metals"— Presentation transcript:
1Comparison of Properties Ionic Compounds Covalent Compounds Metals Chemical BondingComparison of PropertiesIonic CompoundsCovalent CompoundsMetals
2Essential QuestionsWhy/How do atoms combine with one another to form the vast array of chemical substances that exist?What is ionic, covalent and metallic bonding and how do the types of bonding determine properties of matter?
3Properties of MatterMacroscopic properties of matter vary greatly due to the type of bonding
4What is a chemical bond?An attractive force that holds two atoms togetherCan form byThe attraction of positive ion to a negative ion orThe attraction of the positive nucleus of one atom and the negative electrons of another atom
5Bondthe interaction between two or more atoms that allows them to form a substance different from the independent atoms.involves the outer (valence) electrons of the atoms.These electrons aretransferred from one atom to another or shared between them.
6Chemical Bond Energy Considerations A chemical bond forms when it is energetically favorablewhen the energy of the bonded atoms is less than the energies of the separated atoms.Al + I2https://www.youtube.com/watch?v=XBPqSuIN-3E
7BondingChemical compounds are formed by the joining of two or more atoms.A stable compound occurs when the total energy of the combination has lower energy than the separated atoms.The bound state implies a net attractive force between the atoms ... a chemical bond.
8Energy Changes in Bonding When bonds are formed, energy is released.Demonstrations:Formation of an Ionic Compound: Mg + O2Formation of a Molecular Compound: S + O2
9Breaking BondsIn order to break bonds energy must be added, usually in the form of heat, light, or electricity.Demonstration: Electrolysis of waterDemo: Decomposition of Nitrogen Triiodide
11Chemical Bonds In chemical bonds, atoms can either transfer or share their valence electrons.
12When atoms transfer electrons Ionic Bonds When one or more atoms lose electrons and other atoms gain them in order to produce a noble gas electron configuration, the bond is called an ionic bond.
13Ionic Bonding metallic atoms tend to lose electrons When they do so, they become positively charged ions which are called cations.Nonmetallic atoms tend to gain electrons to become negatively charged ions which are called anions.These oppositely charged cations and anions are attracted to one another because of their opposite charges.That attraction is called an ionic bond. We often refer to the charge on the ion as the oxidation state of that element.
14Positive Ion (Cation) Formation Negative Ion (Anion) Formation Na has one valence electron.It loses it to Chlorine.Na now has a filled valence shell. (an octet)Becomes positive one in chargeChlorine has seven valence electrons.It gains one electron from Na.Chlorine now has filled octet.Chlorine has a negative one charge. (Chloride ion)Na+1 attracts Cl-1 and forms the ionic bond.
17Ion FormationAll of the elements in Group I have one electron in their outermost energy level.All of these elements can lose that one valence electron.These atoms become cations with a positive one charge.
18Elements in Group II have two electrons in their outermost energy level. So, when these elements lose electrons, they lose two electrons and take on a positive two charge.
19The transition metals and the metals to the right of them generally form more than one ion. We call these elements multivalent. The charges on their ions are not always predictable, although some patterns do exist.A few of the transition elements form only one ion or oxidation state. For example zinc ion, silver ion and scandium ion.Zn2+ zinc ionAg+ silver ionSc3+ scandium ion
20Anions Nonmetals tend to gain electrons. The halogens - fluorine, chlorine, bromine, and iodine - have a strong attraction for electrons.Their outermost energy levels are almost full. There is only room for one more electron in the outer energy levels for each of those atoms. Consequently, the elements fluorine, chlorine, bromine, and iodine will gain one electron, and become anions with a negative one charge.Oxygen, sulfur, and the other elements in that family will gain two electrons.In the next group over, nitrogen, phosphorus and arsenic can take on three electrons.
22Ionic Nomenclature Naming Ionic Compounds Video of the Process
23Ionic Compounds Made of cations and anions Metals and nonmetals The electrons lost by the cation are gained by the anionThe cation and anions surround each otherSmallest ratio of ions in an ionic compound is a FORMULA UNIT.
24K+1 Ca+2 Cations Positive ions Formed by losing electrons More protons than electronsusually MetalsK+1Has lost one electronCa+2Has lost two electrons
25F-1 O-2 Anion A negative ion Has gained electrons Non metals Charge is written as a super script on the right.F-1Has gained one electronO-2Has gained two electrons
26Formula UnitThe smallest whole number ratio of atoms in an ionic compound.Ions surround each other so you can’t say which is hooked to which
27Naming Ions We will use the systematic way Cation- if the charge is always the same just write the name of the metalTransition metals can have more than one type of chargeIndicate the charge with a Roman numeral in parentheses
32Write theseSulfide ioniodide ionphosphide ionStrontium ion
33Polyatomic ions Groups of atoms that stay together and have a charge You must memorize these or use an ion sheet… common examplesAcetate C2H3O2-1Nitrate NO3-1Nitrite NO2-1Hydroxide OH-1Permanganate MnO4-1Cyanide CN-1
35Practice with IonsUse the practice worksheet to determine the ions formed.Learn to use your periodic table and pink sheet to determine charges (oxidation state.)
36Binary Ionic Compounds Binary Compounds2 elements.a cation and an anion.To write the names just name the two ions.Easy with Representative elementsGroups 1, 2, 13NaCl = Na+ Cl- = sodium chlorideMgBr2 = Mg+2 Br- = magnesium bromide
37Naming Binary Ionic Compounds with Variably Charged Cations The problem comes with the transition metals (Groups 3-12) since their charge can varyNeed to figure out their chargesThe compound must be neutralsame number of + and – charges.Use the anion to determine the charge on the positive ionCharge of the cation is a Roman numeral in the name
38Example Write the name of CuO Need the charge of Cu O is -2 copper must be +2Copper (II) chloride
39Example Name CoCl3 Cl is -1 and there are three of them = -3 Co must be +3 Cobalt (III) chloride
40Another Example Write the name of Cu2S. Since S is -2, the Cu2 must be +2, so each one is +1.copper (I) sulfide
41Last Example Fe2O3 Each O is -2 3 x -2 = -6 3 Fe must = +6, so each is +2.iron (III) oxide
42Naming Binary Ionic Compounds Write the names of the followingKClNa3NCrNSc3P2PbOPbO2Na2Se
43Ternary Ionic Compounds Will have polyatomic ionsAt least three elementsName the ionsNaNO3CaSO4CuSO3(NH4)2O
45Writing Formulas Given the name write the formula The charges have to add up to zeroWrite down each ion with chargesMake the charges equal by adding subscriptsPut polyatomic ions in parentheses if you need more than one of them
46Writing Formulas Example Write the formula for calcium chloride.
48Write the formulas for these Lithium sulfidetin (II) oxidetin (IV) oxideMagnesium fluorideCopper (II) sulfateIron (III) phosphide
49Write the formulas for these gallium nitrateIron (III) sulfideAmmonium chlorideammonium sulfidebarium nitrate
50Things to look forIf cation has (Roman Numeral), the number is the chargeIf anions end in -ide they are probably off the periodic table (Monoatomic)If anion ends in -ate or -ite it is polyatomic
51Ionic SolidsIonic solids are solids composed of ionic particles (ions).These ions are held together in a regular array by ionic bonding.Ionic bonding results from attractive interactions from oppositely charged ions.In a typical ionic solid, positively charged ions are surrounded by negatively charged ions and vice-versa.The close distance between these oppositely charged particles results in very strong attractive forces.The alternating pattern of positive and negative ions continues in three dimensions.The regular repeating pattern is analogous to the tiles on a floor or bricks on a wall.called the crystal lattice.
52Ionic Compounds Crystalline solids (made of ions) High melting and boiling pointsConduct electricity when melted or dissolved in waterDemo: ElectrolytesMany are soluble in water but not in non-polar liquid
54Common Ionic Compounds NaCl - sodium chloride - table saltKCl - potassium chloride - present in "light" salt (mixed with NaCl)CaCl2 - calcium chloride - driveway saltNaOH - sodium hydroxide - found in some surface cleaners as well as oven and drain cleanersCaCO3 - calcium carbonate - found in calcium supplementsNH4NO3 - ammonium nitrate - found in some fertilizers
58Covalent Network Solids Covalent because combinations of nonmetalsInterconnectedvery hard and brittleInsolubleExtreme melting and boiling pointsDiamond
59Covalent Bondsinvolve the sharing of a pair of valence electrons by two atomsSuch bonds lead to stable molecules if they share electrons in such a way as to create a noble gas configuration for each atom
60Covalent bonding can be visualized with the aid of a Lewis Structure
61Polar Covalent BondsCovalent Bonds in which the sharing of the electron pair is unequalthe electrons spend more time around the more nonmetallic atomIn such a bond there is a charge separation with one atom being slightly more positive and the other more negative……. will produce a dipole moment.
62Types of Covalent bonds Pure Covalent (also called non-polar covalent) bonds are ones in which both atoms share the electrons evenlyBy evenly, we mean that the electrons have an equal probability of being at a certain radius from the nuclei of either atom.Polar covalent bonds are ones in which the electrons have a higher probability of being in the proximity of one of the atomsDetermined by Electronegativity Difference
63Electronegativitythe periodic property that indicates the strength of the attraction an atom has for the electrons it shares in a bond.Atoms with high electronegativities tend to hold tightly to their electrons or to form negative ions.These elements are found to the upper right on the periodic table.Atoms with low electronegativities tend to have a lower attraction for their electrons and may form positive ions.These elements are found to the lower left on the periodic table.
64Pure covalent or Non-polar covalent bond Electronegativity difference of 0.3 or less in between the two atoms.A pure covalent bond can form between two atoms of the same element (such as in diatomic oxygen molecule)or atoms of different elements that have similar electronegativies (such as in the carbon and hydrogen atom in methane).
65Polar Covalent BondA is a pair of electrons shared between two atoms with significantly different electronegativities (from 0.3 to 1.7 difference).These bonds tend to form between highly electronegative non-metals and other non-metals, such as the bond between hydrogen and oxygen in water.
66Ionic BondsIn compounds that have elements with very different electronegativities (greater than 1.7 difference), the electrons can be considered to have been transferred to form ions.
67Many of the properties of a compound, such as solubility and boiling point, depend, in part, on the degree of the polarity of its bonds.
68Examples to Determine Bond Character Using electronegativity in the prediction of the polarity of a chemical bond.sodium bonded to chlorineDifference between the electronegativities of Na(0.9) and Cl(3.0) are so great that they form an ionic bond.The hydrogen molecule (2 H atoms bonded to each other)zero electronegativity difference, form a non-polar covalent bond.
69Bond Character Nonpolar-Covalent bonds (H2) Polar-Covalent bonds (HCl) Electrons are equally sharedElectronegativity difference of 0 to 0.3Polar-Covalent bonds (HCl)Electrons are unequally sharedElectronegativity difference between .3 and 1.7Ionic Bonds (NaCl)Electrons are transferredElectronegativity difference of more than 1.7
70Diatomic Molecules hydrogen gas H2 the halogens: chlorine Cl2fluorine F2bromine Br2iodine I2Nitrogen N2Oxygen O2Pneumonic Device to remember the diatomic molecules: Professor BrINClHOF
71Metals and Metallic Bonding Typical Properties of MetalsMalleableDuctileGood Conductors of Heat and ElectricityGenerally high melting and boiling points
72Metallic BondsThe properties of metals suggest that their atoms possess strong bondsyet the ease of conduction of heat and electricity suggest that electrons can move freely in all directions in a metalThe general observations give rise to a picture of "positive ions in a sea of electrons" to describe metallic bonding.
73Metal Properties Malleable and Ductile Strong and Durable Good conductors of heat and electricity.Their strength indicates that the atoms are difficult to separate… strong bondsbut malleability and ductility suggest that the atoms are relatively easy to move in various directions.The electrical conductivity suggests that it is easy to move electrons in any direction in these materials.The thermal conductivity also involves the motion of electrons. All of these properties suggest the nature of the metallic bonds between atoms. (Electron sea model)
74Metallic Bonding Electron Sea Model Explained by the Electron Sea Modelthe atoms in a metallic solid contribute their valence electrons to form a “sea” of electrons that surrounds metallic cations.delocalized electrons are not held by any specific atom and can move easily throughout the solid.A metallic bond is the attraction between these electrons and the metallic cation.
75Metallic Bonding the Electron Sea Model The more delocalized electrons the stronger the bond
76A mixture of elements that has metallic properties is called an alloy. Two types of alloysAn interstitial alloy is one in which the small holes in a metallic crystal are filled by other smaller atoms.A substitutional alloy is one in which atoms of the original metal are replaced by other atoms of similar size.
77Ionic CompoundsCovalent CompoundsMetallic Compounds-Formed from a combination of metals and nonmetals.-Electron transfer from the cation to the anion.-Opposite charged ions attract each other.-Formed from a combination of nonmetals.-Electron sharing between atoms.-Formed from a combination of metals-“sea of electrons”;electrons can move among atomsSolids at room temperatureCan be solid, liquid, or gas at room temperature.High melting pointsLow melting pointsVarious melting pointsDissolve well in waterDo not dissolve in water (Sugar is an exception)Do not dissolve in water.Conduct electricity only when dissolved in water; electrolytesDo not conduct electricity; non electrolytesConduct electricity in solid form.Brittle, hardSoftMetallic compounds range in hardness. Group 1 and 2 metals are soft; transition metals are hard. Metals are malleable, ductile, and have luster.