Chemical Formulas and Compounds

Common Monatomic Ions Chapter 7 Section 1 Chemical Names and Formulas

Common Monatomic Ions Chapter 7 Section 1 Chemical Names and Formulas

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Chapter 7 Oxyanions Some elements can form more than two types of oxyanions. –example: chlorine can form,, or. In this case, an anion that has one fewer oxygen atom than the -ite anion has is given the prefix hypo-. An anion that has one more oxygen atom than the -ate anion has is given the prefix per-. hypochlorite chlorite chlorateperchlorate

Compound Naming 7 Begins w/ H Use Acid Naming Rules Use Acid Naming Rules Yes Begins w/ Metal Begins w/ Metal Use Ionic Compound Rules Use Ionic Compound Rules No Yes No Begins w/ Nonmetal Begins w/ Nonmetal Use Molecular Compound Rules Use Molecular Compound Rules Yes

Rules for Naming Compounds Ionic Compounds Formed from transfer of electrons Ionic Bonds A.K.A Salts Formed from metals and non-metals Name comes from names of Ions Positive ion comes first Anion ends in “ide” 8

Rules for Naming Compounds Molecular Compounds Formed when atoms share electrons Covalent Bonds Typically formed from non-metals Name comes from atoms and prefixes that indicate amount of elements in molecules mono di tri tetra penta hexa hepta octa Suffix “ide” added to more electronegative element More electronegative element written last Some use common names--Ammonia 9

Rules for Naming Compounds Hydrates are ionic compounds with absorbed water in their structure Name after ionic compound and prefix denoting the number of hydrates CuSO 4 5 H 2 O Copper(II) Sulfate Pentahydrate 10

Rules for Naming Compounds Acids with monotomic anion (HCl) Named after anion Suffix “ic” added to anion Prefix “hydro” added to anion Ends in word acid HClHydrochloric acid 11

Rules for Naming Compounds Acids with polytomic anion Named after anion Suffix “ic” added to anion Ends in word acid Learn all acid names in Table 5, p

Oxidation Numbers Oxidation numbers indicate the general distribution of electrons among bonded atoms AKA: Oxidation States No exact physical meaning unlike ionic charges Can be quite arbitrary Useful in balancing equations and writing formulas 13

Rules Governing Oxidation Numbers 1. The oxidation number of an element in an elementary substance is zero. 2. The oxidation number of a element in a monatomic ion is the charge on the ion 3. Certain elements have the same oxidation number in most compounds a.Group 1 metals are +1 b.Group 2 metals are +2 c.Oxygen is usually -2 d.Hydrogen is usually Oxidation numbers sum to zero (compound) or to the charge (polyatomic ion)

Percent Composition & Empirical Formula

The Percent Composition of a Compound The percent by mass of an element in a compound is the number of grams of the element divided by the mass in grams of the compound, multiplied by 100%. 10.3

The Percent Composition of a Compound –Percent Composition from the Chemical Formula 10.3

The Percent Composition of a Compound –Percent Composition from Mass Data The relative amounts of the elements in a compound are expressed as the percent composition 10.3

Empirical Formulas –The empirical formula gives the lowest whole- number ratio of the atoms of the elements in a compound. 10.3

Empirical Formulas The empirical formula gives the lowest whole-number ratio of the atoms of the elements in a compound. Ethyne (C 2 H 2 ) is a gas used in welder’s torches. Styrene (C 8 H 8 ) is used in making polystyrene. These two compounds of carbon have the same empirical formula (CH) but different molecular formulas. 10.3

Finding Empirical Formula From percent composition: Assume 100g of the substance Calculate the number of moles for each substance Divide number of moles for each by the smallest number of moles to find subscripts

Example A compound is composed of 25.9% nitrogen and 74.1% oxygen. a)Find the empirical formula of the compound b)If the Molar mass of the compound is 216g, find the molecular formula.

Finding Molecular Formula Given the molecular formula mass and percent composition: Calculate the empirical formula Calculate the empirical formula mass Find: molecular formula mass empirical formula mass Multiply the empirical formula by this factor