Presentation on theme: "Chapter 7 Ionic Compounds and Metals"— Presentation transcript:
1 Chapter 7 Ionic Compounds and Metals Section 7.1 Ion formation
2 Chemical BondsA chemical bond is the force that holds two atoms together.Can form by the attraction between the positive nucleus of one atom and the negative electrons of anotherCan form between positive and negative ions
3 Valence Electrons Electrons in the outermost principal energy level Shown in the electron dot structuresOctet rule – atoms will gain, lose or share electrons to obtain 8 valence electronsThe valence electrons determine the bonding properties of the atom
4 Positive Ion Formation A positively charged ion is called a cation.Positive ions are formed when an atom loses one or more valence electronsMetals make positive ions
5 Negative Ion Formation A negatively charged ion is called an anion.Negative ions are formed when an atom gains one or more electrons in its valence shell.Nonmetals make negative ions.
6 7.2: Ionic bonds and ionic compounds Formation of an Ionic Bond An ionic bond is the electrostatic force that holds oppositely charged particles together in an ionic compoundCompounds that contain ionic bonds are called ionic compounds.Ionic compounds are formed betweenmetals (+ charge) and nonmetals (- charge).
7 Binary Ionic Compounds Contain a metallic cation and a nonmetallic anion.Formation of Binary Ionic CompoundsElectron(s) is/are transferred from metal to nonmetalMetal becomes positive, nonmetal becomes negativeOpposite charges attract
8 Properties of Ionic Compounds Take the structure of a crystal latticeMany units of positive and negative ions stick together in a three-dimensional geometric arrangementCan conduct electricity when dissolved in water (they are electrolytes and break into ions when dissolved in water), but not in solid formMelting point, boiling point and hardness depend upon how strongly the ions are attracted to each other
9 Formulas for Ionic Compounds Monatomic ions are one-atom ionsExamples: Mg2+ , Br-1Oxidation numbers are the charges on ionsNote: some elements have multiple oxidation states – you will have a periodic table to tell thisBinary ionic compounds are made of two monatomic ions (one positive, one negative)
10 Formulas for Binary Ionic Compounds Symbol for cation is written first, anion secondSubscripts tell the number of atoms of each elementWhat are the following compounds made of?CaF calcium, 2 fluorineNa2S sodium, 1 sulfurNaCl sodium, 1 chlorine
11 Naming Binary Ionic Compounds Name the cation firstName the anion second with –ide at the endExamplesCaF2 calcium fluorideNa2S sodium sulfideNaCl sodium chloride
12 Try Naming a few more Binary Ionic Compounds K2O potassium oxideAl2S3 aluminum sulfideNa3N sodium nitride
13 What if the cation has more than one oxidation state? You tell which ion was used by putting a Roman Numeral after the name of the cationExample:CuSWe know S was -2 (that’s the only one it makes)If there is only one atom of each element, the Cu must have been +2So, the name is written as Copper (II) sulfide [the “II” indicates the charge]Make sure, especially with transition elements, that you are checking the oxidation states
14 Writing Formulas for Binary Ionic Compounds Look up the charges for each elementFor a compound to form, the total charge must balance out to zero (positive charges must equal negative charges)Example:Sodium bromideNa is +1, Br is -1Only need one of each to balanceFormula is NaBr
15 Try writing some more formulas Binary Ionic Compounds Potassium Iodide KIAluminum bromide AlBr3Magnesium chloride MgCl2Cesium nitride Cs3N
16 Formulas for Polyatomic Ionic Compounds Polyatomic ions are ions that are made up of more than one atomYou will have a chart for these and do not have to memorize them.Examples:SO42- = sulfateCN- = cyanideNH4+ = ammonium
17 Naming Polyatomic Ionic Compounds Name the cation first, anion secondName the polyatomic as is – don’t change its name at allExamples:Ca3(PO4)2 calcium phosphateMg(CN)2 magnesium cyanideNH4Cl ammonium chloride
18 Now you try naming Polyatomic Ionic Compounds NaNO3 sodium nitrateCa(ClO3)2 calcium chlorateAl2(CO3)3 aluminum carbonate
19 Writing formulas for Polyatomic Ionic Compounds Same as binary ionic compounds EXCEPT you may not change anything in the polyatomic ion formulaPut them in a (parenthesis) and put subscripts outside that parenthesisExample:Calcium NitrateIons are Ca2+ and NO3-Formula will be Ca(NO3)2
20 Now you try writing formulas for Polyatomic Ionic Compounds Sodium hydroxide NaOHCopper (II) nitrate Cu(NO3)2Silver chromate Ag2CrO4
21 7.3: Metallic bonds and the properties of metals The electron sea model proposes that all the metal atoms in a metallic solid contribute their valence electrons to form a “sea” of electronsSince the electrons are free to move, they are called delocalized electronsA metallic bond is the attraction of a metallic cation for delocalized electrons
22 Properties of Metals (revisited) Moderately high melting pointsHigh boiling pointsMalleable, ductile, durableConduct heat and electricity wellTransition metals are harder/stronger than alkali metals because the transition metals have more delocalized electrons
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