Ionic Compounds and Metals

IMPORTANT! Some things you MUST know to be successful…. You really need to commit these things to memory

Ions: A Refresher Atoms or groups of atoms with a charge. Cations- positive ions - get by losing electron(s). Anions- negative ions - get by gaining electron(s). Ionic bonding- held together by the opposite charges- electrostatic attractions. Ionic solids are called salts. Salts are electrolytes; they conduct electricity when dissolved in water (aq.)

Common Ions of Elements +1 +3 +/-4 +2 -3 -2 -1 Variable, always +

Predicting Charges on Monatomic Ions KNOW THESE !!!! +1 +2 -3 -2 -1 0 Cd+2

Polyatomic Ions Groups of covalently bonded atoms that have a charge. * NO3- :nitrate ion * NO2- :nitrite ion Yes, you have to memorize them. Listed in your resource handbook: memorize the required list!!!!

Patterns for Polyatomic Ions -ate ion chlorate = ClO3- -ate ion plus 1 O  same charge, per- prefix perchlorate = ClO4- -ate ion minus 1 O  same charge, -ite suffix chlorite = ClO2- -ate ion minus 2 O  same charge, hypo- prefix, -ite suffix hypochlorite = ClO- 14

Polyatomic Ions You can make additional polyatomic ions by adding a H+ to the ion! CO3 -2 is carbonate: HCO3– is hydrogen carbonate PO43- is phosphate: HPO42- is hydrogen phosphate H2PO4– is dihydrogen phosphate SO42- is sulfate HSO4– is hydrogen sulfate

The 3 types of Chemical Bonds: Ionic, Covalent, & Metallic How do they bond? Will gain, share or lose electrons Why do they bond? Gain stability Full outer shell Lower energy = more stable Depend on what is bonding .

The 3 types of Chemical Bonds: Ionic, Covalent, & Metallic Electronegativity and Bond type Bond type can be determined by the difference in electronegativity between the bonds involved. Differences of: ≥ 2 = ionic 0.5 – 1.9 = polar covalent ≤ 0.4 = nonpolar covalent Metals bonded to other metals are metallically bonded, regardless of the difference in electronegativity .

Metallic bonds The atoms of metals are held together when the atom’s valence electrons float around the nuclei of the metals – the “sea of electrons” Electrostatic forces keep everything together

Metallic bonds The valence electrons are not held by any specific atom The e-’s can move easily from 1 atom to the next so they are called delocalized electrons

Properties of metals Moderately high melting and boiling points Malleable and ductile and durable Good conductors of electricity and heat Interact with light creating luster Hardness and strength increase as more e-’s are added (in d orbitals). Mix together to form alloys

Ionic Bonds: Complete transfer of 1 or more electron from one atom to another (or another group) one loses one or more e-, the other gains those e- Atoms involved are a metal and either a non-metal or a polyatomic ion The cation and anion are attracted to each other by electrostatic attraction .

Ionic compounds are neutral That is, they have no overall charge This is because the number of electrons that are given up by the metal is the same number of electrons that are gained by the anion for the formula. Formulas reflect this neutrality- the charges on the individual ions are not written in because they cancel out overall for the compound

COMPOUNDS FORMED FROM IONS CATION + ANION ---> COMPOUND Na+ + Cl- --> NaCl A neutral compound requires equal number of + and - charges.

Properties of Ionic compounds Ions are packed together in a regular repeating pattern Highly organized Consistent spacing and pattern 3-D arrangement of particles is a crystal lattice In aqueous solution (dissolved in H2O) Ions dissociate Can conduct a current so it’s know as an electrolyte

Properties of Ionic compounds Hard and rigid but brittle Formation is always exothermic The energy needed to break apart the crystal lattice in ionic compounds is lattice energy Higher lattice energy = stronger forces holding ions together Affected by size (smaller atoms = closer = higher lattice energy) and charge (larger positive or negatives = greater lattice energy)

Covalent Bonds 2, 4, or 6 valence electrons that are shared between atoms We are going to name only simple covalent compounds that have 2 elements involved

Most bonds are somewhere in between ionic and covalent Because not all atoms share e- equally The conventions of naming assume absolute difference in bond types Metals bonded to nonmetals or polyatomic ions are classified as having ionic bonds* Materials made out of all non-metals are classified as having covalent bonds* * semimetals are not a classification in naming; you need to treat the elements that are on the right of the line as non-metals, and those on the left as metals. More on this when we talk about bonding

Naming things: Is there a metal first? If there is only one element present, name it. Atomic substances do not require “special” naming. For anything with more than one element, remember that there is ONE MAIN THING to look for: Is there a metal first?

So… Look to see if there is a metal first in the formula Again, semimetals are not a classification in naming; you need to treat the elements that are on the right of the line as non-metals, and those on the left as metals. If there are only metals, name both metals (metallic bonding; nothing else need be done) If ONLY the first element is a metal, then the compound is an ionic compound Nonmetals only signify a covalent compound There is a flow chart in your handbook to help!

Naming ionic compounds: Remember that those are compounds that have a metal first in the formula*, and then a nonmetal or a polyatomic ion. *Two exceptions to this rule: Compounds that start with either ammoniums (NH4+) or hydronium (H3O+) We can handle these as simple binary (2 elements) and ternary (more than two elements) compounds

General information for naming ionic compounds If the cation is monatomic- Name the metal (cation). Use Roman Numerals for transition metals (ONLY) after the metal If the cation is polyatomic- name it. If the anion is monatomic- name it but change the ending to –ide. If the anion is poly atomic- just name it.

Ternary Ionic Compounds: Contain at least 3 elements There MUST be at least one polyatomic ion (it helps to circle the ions) Examples: NaNO3 Sodium nitrate K2SO4 Potassium sulfate Al(HCO3)3 Aluminum bicarbonate (Aluminum hydrogen carbonate)

If the Metal is a Transition Metal… Transition metals are Type II Cations, and are elements that can have more than one possible charge. They MUST have a Roman Numeral to indicate the charge on the individual ion. 1+ or 2+ 2+ or 3+ Cu+, Cu2+ Fe2+, Fe3+ copper(I) ion iron(II) ion copper (II) ion iron(III) ion

Type II Cations (have transition metals) These elements REQUIRE Roman Numerals because they can have more than one possible charge: anything except Group 1A, 2A, Ag, Zn, Cd, and Al (You should already know the charges on these!) Or another way to say it is: Transition metals and the metals in groups 4A and 5A (except Ag, Zn, Cd, and Al) require a Roman Numeral. FeCl3 (Fe3+) iron (III) chloride CuCl (Cu+ ) copper (I) chloride SnF4 (Sn4+) tin (IV) fluoride PbCl2 (Pb2+) lead (II) chloride Fe2S3 (Fe3+) iron (III) sulfide You will appreciate this more when we go from names to formulas!

Type II Cations Some Type II cations have a name using the “old” system as well as the “new system”. The old system, still widely used, adds to the root or stem of the Latin name of the metal the suffixes –ous and –ic. These represent the lower and higher charges respectively.

Examples of Older Names of Cations formed from Transition Metals (you do not have to memorize these)

General naming rules for covalent compounds Names are two words, with prefixes. Prefixes tell you how many. First element whole name with the appropriate prefix, except mono. Second element, -ide ending with appropriate prefix.

Covalent Naming Prefixes: mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca- NUMBER 1 2 3 4 5 6 7 8 9 10

Common Names A lot of chemicals have common names as well as the proper IUPAC name. Chemicals that should always be named by common name and never named by the IUPAC method are: H2O water, not dihydrogen monoxide NH3 ammonia, not nitrogen trihydride

Hydrates: Ionic Compounds·Water Some salts trap water crystals when they form crystals. Ex: CuSO4· 5H2O These are hydrates. Both the name and the formula needs to indicate how many water molecules are trapped. In the name we add the word hydrate with a prefix that tells us how many water molecules. CuSO4· 5H2O is copper (II) sulfate pentahydrate

Hydrates In the formula you put a dot and then write the number of water molecules. Calcium chloride dihydrate = CaCl2·2H2O Chromium (III) nitrate hexahydrate = Cr(NO3)3· 6H2O

Acid Nomenclature Acids Compounds that form H+ in water. Formulas usually begin with ‘H’. In order to be an acid instead of a gaseous covalent compound, it must be aqueous Meaning dissolved in water; symbolized by (aq) Ternary acids are ALL aqueous Two types: Oxyacids Non-oxyacids

Acid Nomenclature Flowchart

Acid Nomenclature An easy way to remember which goes with which… Binary  Ternary An easy way to remember which goes with which… “In the cafeteria, you ATE something ICky”

Acid Nomenclature HBr (aq) H2CO3 (aq) H2CO2 (aq)  hydrobromic acid 2 elements, -ide  hydrobromic acid 3 elements, -ate  carbonic acid 3 elements, -ite  carbonous acid

Acid Name HNO3 Nitric acid HNO2 Nitrous acid H2SO4 Sulfuric acid H2SO3 Sulfurous acid H3PO4 Phosphoric acid HC2H3O2 Acetic Acid

Writing Formulas for Ionic Compounds from Names Formulas of ionic compounds are determined from the charges on the ions Na + F  Na+ + F-  NaF Sodium atom + fluorine atom sodium fluoride Charge balance: 1+ + 1- = Symbols represent elements. Formulas describe compounds. Remember that all ionic compounds have no net charge, and that the charges are not written in! Ever. Nope.

Neutral, you say? Formulas are written to make the compound have a neutral charge overall. You do NOT write the charges in the formula because they MUST cross out to accurately represent the compound. Ex: NaF2 is INCORRECT for sodium chloride because Na has an oxidation state of +1, and F of -1. There is a one to one ratio of Na+ to F- to make a neutral ionic compound.

So what if the oxidation numbers aren’t even? If the oxidation numbers or charges do not balance, you can write the number of ions of each until you get the same number of each charge in total. Yes. The “Criss Cross” method. You take the charge number from the cation, and you make it the number of anions, and take the charge on the anion, and you make that many cations. Is there an easier way?

Criss-Crossing in action: Example: Lead (II) nitrate Pb2+ N3- *the charges do not balance Pb2+ N3- Pb3N2 The 2 and the 3 are brought down to the opposite element, so that there are now 3 Pb2+ ions and 2 N3- ions This means there were 6e- transferred from the lead atoms to the nitrogen atoms; the compound is neutral

Writing Formulas for Ternary Ionic Compounds Write the cation first, then the anion. Overall charge must equal zero. If charges cancel, just write symbols. If not, use subscripts to balance charges. Use parentheses to show more than one of a particular polyatomic ion. Use Roman numerals indicate the ion’s charge when needed (transition metals) Remember that the final formula should not have charges written in.

Writing Formulas with Polyatomic Ions Example: Cr2+ PO43- *the charges do not balance Cr2+ PO43- Cr3(PO4)2 The polyatomic ions is in parentheses whenever a subscript is added This is so that we know to count a number of those groups!

You NEVER criss-cross charges with covalent compounds. Since you are sharing electrons, rather than giving them away/ picking them up, the charges are not relevant.

Covalent Naming Prefixes: mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca- NUMBER 1 2 3 4 5 6 7 8 9 10

Formulas for acids Backwards from names. If it has hydro- in the name it has no oxygen Anion ends in -ide No hydro, anion ends in -ate or -ite Write anion and add enough H to balance the charges.

Rainbow Matrix Game Link on Chemistry Geek.com on Chemistry I page http://chemistrygeek.com/rainbow Use [ ] to represent subscripts since you can’t enter subscripts into the computer So H2O would be H[2]O And Al2(SO4)3 would be Al[2](SO[4])[3] Additional Polyatomic Ions (you do not have to memorize these, but they are in the game!) Borate = BO3 -3 ; Silicate = SiO4 -4 ; Manganate = MnO4 -2 (permanganate is -1)