Goals for Today 0 Be able to draw Lewis Dot Diagrams for atoms, ions and ionic compounds 0 Be able to write the names of ionic compounds 0 Be able to write the formulas for ionic compounds 0 Today we are only working with binary ionic compounds.
Let s review the structure of an atom Nucleus contains protons and neutrons Electrons are found in energy levels that surround the nucleus, called shells. Each shell or energy level can hold a certain number of electrons. 1 st shell 2 electrons 2 nd shell 8 electrons Goal of atoms is for the outermost energy level to be full like the noble gases Non-metals do this by sharing electrons: covalent bond. Metals do this by donating electrons to non-metal ions: ionic bonds
How can we show the number of outermost electrons in an atom?
Electron Dot Formulas (Lewis Dot Structures) Representations of atoms or molecules where dots surround each atom s symbol showing the outermost electrons (valence electrons) Rules for writing these formulas: 1. Maximum of 2 dots per side 2. Only pair dots if more than 4 electrons 3. No more than 8 electrons around any element.
How this works Hydrogen Carbon H C
Ionic Compounds
Electrical Nature of Matter Neutral Atom Equal # of protons and electrons Charged Atom Unequal # of protons and electrons - More electrons then protons + More protons then electrons
Ions Electrically charged atoms or group of atoms Practice drawing the following ions: Na +1 Cl -1 B +3 O -2
Ionic Compounds Occur when one element in a compound has a stronger attraction to valence electrons than the other element. Usually occurs between a metal and a nonmetal
Draw Ionic Compounds Draw the following: NaCl CaF 2 K 2 O MgO
NaCl and CaF2
Naming a Binary Ionic Compound If the compound is made up of only 2 elements : 1. Name the first element first 2. Name the second element next but change the ending of the name to ide * Subscripts do not matter! Examples: NaCl BaF 2 Na 2 O K 2 S
Naming an Ionic Compound If the compound has a metal with multiple possible charges follow the following with a multi valence metal 1. The first element listed is a metal, look at your periodic table, does the metal have more than one charge, if so you MUST indicate the charge of the metal using roman numerals. How can you do that? You must figure it out from what it is bonded with. 2. Name the second element next, if it is a single element change the ending of the name to ide. If it is a polyatomic ion, then name it.
Naming an Ionic Compound with a multi valence metal Fe 2 O 3 FeO AuCl AuCl 3
Ionic Formulas 0 The goal with ionic formulas is to make the charges on the ions equal to zero (getting a neutral compound.) 0 To do this we must figure out how many of each ion is needed so that when all the charges are added together their sum comes out to be zero. 0 Criss-Cross method. 0 Write out the symbols and charges for each ion in the compound 0 If charges don t add up to zero, then criss-cross the NUMBER ONLY from the charge and that becomes the subscript on the opposite ion.
Ion Formula Examples 0 Magnesium Sulfide 0 Strontium Phosphide 0 Iron (III) Bromide
Polyatomic Ions 0 Polyatomic ions are ions made up of two or more atoms. (usually two non-metals combined) 0 Lewis Dot Diagrams for Polyatomics: SO 3 2- SO 4 2-
Names and Formulas 0 Naming ionic compounds with polyatomic ions: 0 Name the first element (use roman numerals if needed) 0 Name the second ion (polyatomic) BUT DON T change the ending leave it like you see it from the chart. 0 Formula Writing: 0 Write both ions next to each other with charges in the corners 0 Check to see if the charges add up to zero. 0 If NO Then use criss-cross method. Put polyatomic ion in parentheses and place the subscript on the outside.
Polyatomic Naming Practice 0 NaOH 0 MgSO 4 0 NH 4 NH 3 0 Pb(NO 3 ) 2
Polyatomic Formula Practice 0 Calcium Hydroxide 0 Cobalt (II) Cyanide 0 Lithium Phosphate