explain with examples how different metals react with oxygen at different temperature
Answers
Oxygen is ubiquitous; it comprises approximately 46% of the crust, 21% of the atmosphere, and 61% of the human body. Because of oxygen's high reactivity, it is most often found in compounds. Oxygen's high reactivity is due to its biradical electron configuration. As shown in a molecular orbital drawing of O2, the two unpaired electrons make the molecule highly susceptible to bond formation.
Oxygen has two allotropes (dioxygen, O2, and ozone, O3), both excellent oxidizing agents (Table P2). Oxygen is typically observed observed in the -2 oxidation state, in the form O2-, but it can also form other ions such as peroxide, O22-, and superoxide, O2-. With different possible oxidation states, many possible molecular compounds can be formed when an element reacts with oxygen. Many reactions involving oxygen occur in biological processes, including cellular respiration and photosynthesis.
Oxides are chemical compounds that contain at least one oxygen atom and at least one atom of another element. There are four principle oxidation states of oxygen: -2, -1, -1/2, and 0. The oxide ion, O2-, has a oxidation state of -2; the peroxide ion, O22-, has a oxidation state of -1; and the superoxide ion, O2-, has a oxidation state of -1/2. With metals, oxygen forms oxides that are largely ionic in character.
There are general trends in the reactions between main group elements and oxygen:
Most nonmetals form the oxide with the highest possible oxidation state, with the halides excepted. Most metals form oxides with the oxygen in a -2 oxidation state.As a general rule, metal oxides are basic and nonmetal oxides are acidic. Basicity of an oxide increases with increasing ionic (metallic) character. Metal oxides, peroxides, and superoxides dissolve in water actually react with water to form basic solutions. Oxygen also forms covalent oxides with non-metals, that react with water to form acidic solutions. Oxygen does not react with fluorine or noble gases.