Chapter 22 - Periodicity 2 Flashcards
How do Na and Mg react with water?
Sodium is readily reactive with water, fizzing by releasing hydrogen, and forming sodium hydroxide.
Magnesium reacts instead slowly with cold water to form magnesium hydroxide, however it will react much faster with steam to give magnesium oxide and hydrogen instead
What are the formulae of the reactions of period 3 elements with oxygen?
Na2O, reacts readily with a characteristic yellow flame
Magnesium burns very brightly and forms MgO
Al2O3, aluminium is a very reactive metal, however it forms an oxide coating which is strongly bound to the metal underneath, making aluminium appear unreactive
Silicon needs to be heated strongly to form SiO2
Phosphorus (depending on its form) will readily react with oxygen to form P4O10, however in a lack of oxygen P2O3 may form
Sulfur will react at a fairly low temperature to form SO2, however at a very high temperature and pressure it will make SO3, the precursor to sulfuric acid
What are the physical properties of the period 3 oxides?
Sodium, magnesium and aluminium all form ionic lattices due to the metal - nonmetal bond. However, aluminium is so small and highly charged it is able to exhibit some covalent character. Silicon is macromolecular, however phosphorus and silicon exist as molecules. The phosphorus oxides are solid at room temperature due to the existence of some dipole-dipole interaction, however sulfur dioxide and trioxide are both gases at room temperature
Reactions of period 3 oxides with water?
Sodium and magnesium will react to form hydroxides, sodium being very soluble with a pH of 14, however magnesium will be sparingly soluble so a pH of about 9. Aluminium oxide and silicon oxide are insoluble, however phosphorus pentoxide is very soluble in water and reacts violently to form phosphoric (V) acid. Silicon dioxide can react with water fairly easy to form sulfurous acid, which partially dissosciates resulting in a mildly acidic solution. SO3 however very easily reacts to form the very acidic sulfuric acid
What is the behaviour of period 3 oxides with acids or bases?
The first 2 will both act as bases. Aluminium however, acts amphoterically, being both a base and an acid depending on the conditions. Silicon oxide will act as a weak acid for strong bases, and phosphorus and sulfur dioxide will both act as acids and neutralise bases
