» Binary molecular compounds ˃Composed of two nonmetal elements » No ions are present, just molecules, therefore ionic charge cannot be used to write names or formulas » If we named molecular compounds as though they were ionic compounds there would be no way to differentiate between two or more compounds with the same elements in different ratios.

» We use prefixes in the name of binary molecular compounds to differentiate between compounds with different amounts of the same elements. » The prefixes tell us how much of each element are present in 1 molecules of the compound Table 9.4 Prefixes Used in Naming Binary Molecular Compounds PrefixMono-Di-Tri-Tetra-Penta-Hexa-Hepta-Octa-Nona-Deca- #

» Confirm that the compound is a binary molecular compound » The name must identify the elements in the molecule and the number of each atom » Use prefixes to indicate the number of atoms » If there is only 1 atom of the first element, do not use a prefix (OMIT MONO-) » The second element should always have a prefix. » The central atom is generally written first. » The suffix of the 2 nd element will always be –ide.

» Examples ˃CO  carbon monoxide ˃N 2 O  dinitrogen monoxide ˃Cl 2 O 8 <-- dichlorine octoxide ˃SF 6  sulfur hexafluoride

» To write the formula of a binary molecular compound: ˃Use the prefix in the name to tell you the subscript of each element in the formula. ˃Write the correct symbols for the two elements with the appropriate subscripts. Examples Silicon carbide  there are no prefixes therefore there is 1 of each atom in 1 molecule of the compound SiC Dinitrogen tetroxide  di = 2, tetra = 4 N 2 O 4

» Acid – a compound that contains one or more hydrogen atoms and produces H + when dissolved in water » To name an acid: ˃Think of the components of an acid as an anion and as many hydrogen ions that are needed to balance the charge of the anion. (you are making the molecule electrically neutral.) » the general form of the chemical formula of an acid is H n X » n = the number of hydrogen ions combined with the anion » X = a monatomic or polyatomic anion

» (aq) must appear after the formula to be named as an acid » Study these examples, and determine the rules for naming acids: HCl (aq)hydrochloric acid H 3 PO 4 (aq)phosphoric acid HNO 3 (aq)nitric acid HClO (aq)hypochlorous acid H 2 S (aq)hydrosulfuric acid Hint: relate the name of the anion, to the name of the acid. HI(aq)hydroiodic acid H 2 SO 4 (aq)sulfuric acid HNO 2 (aq)nitrous acid H 2 Se (aq)hydroselenic acid HC 2 H 3 O 2 (aq)acetic acid

» Two types of acids: polyatomic anions ˃_________ -ic acid (anion ends in –ate) ˃_________ -ous acid (anion ends in –ite) monatomic anions ˃hydro_________ -ic acid » The root of the anion name goes in the blank To write the formula for an acid, use the naming rules in reverse.

» Bases: A group of ionic compounds, that produce OH - ions when dissolved in water. » Name them just like any other ternary compound. Look back at the previous packet for naming ionic compounds.

» Hydrated compounds are ionic compounds that have water molecules “trapped” within the crystal structure » BaCl 2. 2H 2 O The “dot” does not mean multiply! It is just a symbol that connects the water molecules to the ionic formula unit.

» Name the ionic piece, then use a prefix in front of the word “hydrate” to complete the name. » BaCl 2. 2H 2 Obarium chloride dihydrate

» We know that  compounds form in predictable ways » Mass measurements were used to deduce this fact

» In samples of any chemical compound, the masses of the elements are always in the same proportions » In a sample of NaCl there is a fixed mass ratio of sodium to chlorine. » 39 g of Na and 61 g of Cl in a 100 g sample of NaCl. » This reduces to a Na:Cl ratio of : 1. » This ratio is observed, no matter the size of the sample. This empirical fact led to the conclusion that if mass ratios are fixed, then atom ratios must be fixed, also.

» This law deals with compounds that form in more than one ratio. » Can you think of any examples of this? » Lead forms two compounds with oxygen? Calculate the Pb:O ratio for each sample. Compound A 2.98 g Pb0.461 g O Compound B 9.89 g Pb0.763 g O

Compound A: 6.46:1Compound B: 12.96:1 » The mass ratios of Pb are 6.46 : 12.96, or 1: 2, in the two compounds. » Whenever a compound of 2 elements forms in multiple ratios, a whole-number ratio of masses is observed. » If the masses increase in whole-number ratios, then the atoms must increase in whole-number ratios as well.