Molecular Compounds Section 9.3

Molecular Compounds A prefix in the name of a binary molecular compound tells how many atoms of an element are present in each molecule of the compound. Carbon monoxide CO Carbon dioxide CO2

Writing Formulas for Binary Molecular Compounds Use the prefixes in the name to tell you the subscript of each element in the formula. Then write the correct symbols for the two elements with the appropriate subscripts. Silicon carbide SiC Dinitrogen tetroxide N2O4

Naming Acids Section 9.4

Naming Acids When the name of the anion (X) ends in -ide, the acid name begins with the prefix hydro-. The stem of the anion has the suffix -ic and is followed by the word acid. Therefore, HCI(aq) (X =chloride) is named hydrochloric acid, H2S (aq) ( X = sulfide) is named hydrosulfuric acid.

When the anion name ends in –ite, the acid name is the stem of the anion with the suffix -ous, followed by the word acid. Thus H2SO3 (aq) (X = sulfite) is named sulfurous acid.

3. When the anion name ends in -ate, the acid name is the stem of the anion with the suffix -ic followed by the word acid. Thus HNO3 (aq) (X = nitrate) is named nitric acid.

Laws Governing Formulas & Names Section 9.5

Law of Definite Proportion • In any sample of a chemical compound the masses of the elements are always in the same proportion

Law of Definite Proportion • This ratio does NOT change based on the size of the sample or how it was formed CO l2gC to l6gO Ratio 3 to 4

• This is consistent with Dalton’s Atomic Theory • Atoms combine in simple whole number ratios

• Dalton studied compounds that contain same elements • CO and CO2 • Both obey Law of Definite Proportion

• CO 12g C to 16g O •CO2 l2g C to 32g O 32g O (in CO2 per 12g C) = 2 16g O (in CO per 12g C) 1 • = 2: 1 ratio ****

Law of Multiple Proportions Whenever two elements form more than one compound, the mass of one element compared to a fixed mass of another element is a ratio of small whole numbers