In Group 1, lithium nitrate behaves in the same way, producing lithium oxide, nitrogen dioxide, and oxygen as shown: \[ 4LiNO_3 (s) \rightarrow 2Li_2O (s) + 4NO_2 (g) + O_2 (g)\]. You will find some information about the nitrates, carbonates, hydrogencarbonates and hydrides of the metals. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. It is also difficult to get reliable results if you heat these carbonates in the lab. For the purposes of this topic, you don't need to understand how this bonding has come about. The thermal stability of the hydrogencarbonates. The polarization argument exactly the same for these compounds. For example, a typical Group 2 nitrate like magnesium nitrate decomposes this way: \[ 2Mg(NO_3)_2 (s) \rightarrow 2MgO(s) + 4NO_2 (g) + O_2 (g)\]. This is too difficult to talk about at this level - and I'm not going to do it! The other Group 1 hydrides can be electrolyzed in solution in various molten mixtures such as a mixture of lithium chloride and potassium chloride. If you have read the section on Group 2 of the Periodic Table, you may know that I have shown why the usual explanations given for these trends at this level don't work. Relevance. In Group 2, the most soluble is barium hydroxide—it is only possible to make a solution of concentration around 3.9 g per 100 g of water at the same temperature of 20°C . Solubility of the carbonates increases as you go down Group 1. Solubility of the sulphates. The carbonates tend to become less soluble as you go down the Group. If the positive ion only has one positive charge, the polarizing effect is lessened. These are made by passing hydrogen gas over the heated metal. The shading is intended to show that there is a greater chance of finding them around the oxygen atoms than near the carbon. The hard way is in terms of the energetics of the process; the simple way is to look at the polarising ability of the positive ions. On heating, most of these hydrides decompose back into the metal and hydrogen before they melt. For example, this is the reaction for sodium hydrogen carbonate: \[ 2NaHCO_3 (s) \rightarrow Na_2CO_3 (s) + CO_2 (g) + H_2O (l)\]. The decomposition temperatures again increase as you go down the Group. As the positive ions get bigger down the group, they have less effect on the carbonate ions near them. For example, sodium hydride reacts with water to produce sodium hydroxide and hydrogen gas: The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. For example, a typical Group 2 carbonate like calcium carbonate decomposes like this: \[ CaCO_3 (s) \rightarrow CaO(s) + CO_2 \]. By contrast, the least soluble Group 1 carbonate is lithium carbonate. Magnesium carbonate (the most soluble one I have data for) is soluble to the extent of about 0.02 g … You will often find that the lithium compounds behave similarly to Group 2 compounds, but the rest of Group 1 are in some way different. Unit 1: THE LANGUAGE OF CHEMISTRY, STRUCTURE OF MATTER AND SIMPLE REACTIONS. You will need to use the BACK BUTTON on your browser to come back here afterwards. The amount of heat required depends on how polarized the ion was. The carbonate ion becomes polarised. Most carbonates tend to decompose on heating to give the metal oxide and carbon dioxde. There are two ways of explaining the increase in thermal stability down the Group. By contrast, the Group 1 hydrogen carbonates are stable enough to exist as solids, although they do decompose easily on heating. papastolte. For example, for lithium hydride: These are limited to the two reactions most likely to be wanted by UK A level syllabuses. This page discusses a few compounds of the Group 1 elements (lithium, sodium, potassium, rubidium and cesium), including some information about the nitrates, carbonates, hydrogen carbonates and hydrides of the metals. Exactly the same arguments apply to the nitrates or hydrogencarbonates. (ii) Carbonates. The next diagram shows the delocalised electrons. Hydrogen is given off at the anode (the positive electrode); this is convincing evidence for the presence of the negative hydride ion in lithium hydride. The thermal stability of the hydrogen carbonates, Explaining the trends in thermal stability, Explaining the trend in terms of the polarizing ability of the positive ion, Extension to nitrates and hydrogen carbonates. Because they can react violently with water or moist air, they are normally supplied as suspensions in mineral oil. Lv 6. What about the nitrates and hydrogencarbonates? A bigger positive ion has the same charge spread over a larger volume of space. These mixtures melt at lower temperatures than the pure chlorides. The hydroxides The least soluble hydroxide in Group 1 is lithium hydroxide, but it is still possible to make a solution with a concentration of 12.8 g per 100 g … Solubility of the carbonates increases as you go down Group 1. Solution: Solubility of carbonates decreases on moving down the group as hydration energy decreases. They have the same crystal structure as sodium chloride, which is why they are called saline or salt-like hydrides. The small positive ions at the top of the Group polarize the nitrate or hydrogen carbonate ions to a greater extent than the larger positive ions at the bottom. 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