Tham khảo sách 'chemistry part 12, julia burdge,2e (2009)', khoa học tự nhiên, hoá học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 266 CHAPTER 7 Electron Configuration and the Periodic Table TABLE Na2O MgO AI2O3 SÎO2 P4O10 SO3 C 2O7 Type of compound Ionic Molecular Structure ------------Extensive three-dimensional------------ Discrete molecular units Melting point C 1275 2800 2045 1610 580 Boiling point C 3600 2980 2230 82 Acid-base nature Basic Basic Amphoteric Acidic Certain oxides such as CO and NO are neutral that is they do not react with water to produce acidic or basic solutions. In general oxides of nonmetals are either acidic or neutral. SiO2 also has a huge three-dimensional network although it is not an ionic compound. The oxides of phosphorus sulfur and chlorine are molecular compounds composed of small discrete units. The weak attractions among these molecules result in relatively low melting points and boiling points. Most oxides can be classified as acidic or basic depending on whether they produce acids or bases when dissolved in water or whether they react as acids or bases . Some oxides are amphoteric which means that they display both acidic and basic properties. The first two oxides of the third period Na2O and MgO are basic oxides. For example Na2O reacts with water to form the base sodium hydroxide Na2O s H2O Z ------ 2NaOH a Magnesium oxide is quite insoluble it does not react with water to any appreciable extent. However it does react with acids in a manner that resembles an acid-base reaction MgO s 2HCl u ------- MgCl2 H2O Z The products of this reaction are a salt MgCl2 and water the same kind of products that are obtained in an acid-base neutralization. Aluminum oxide is even less soluble than magnesium oxide. It too does not react with water but it exhibits the properties of a base by reacting with acids A12O3 5 6HC1 ------- 2A1C13 3H2O Z It also exhibits acidic properties by reacting with bases A12O3 s 2NaOH a 3H2O Z -------- 2NaAl OH 4 Thus A12O3 is classified as an amphoteric oxide because it has properties of both acids and bases. Other .
