(3 Marks) (c) Draw The Molecular Orbital Diagram For Peroxide Ion. You could argue that the activation energy will fall as you go down the Group and that will make the reaction go faster. It is also reluctant to start burning, but then burns with an intense almost white flame with red tinges especially around the outside. In all the other cases in Group 1, the overall reaction would be endothermic. As you go down the Group and the positive ions get bigger, they don't have so much effect on the peroxide ion. 2.11 Group II elements and their compounds. Those reactions don't happen, and the nitrides of sodium and the rest aren't formed. While it would be tempting to say that the reactions get more vigorous as you go down the Group, but it is not true. The general equation for the Group is: \[ 3X_{(s)} + N_{2(g)} \rightarrow X_3N_{2(s)}\] Lithium is the only metal in Group 1 to form a nitride. It cannot be said that by moving down the group these metals burn more vigorously. Reaction with water Most Group II oxides react with water to produce the hydroxide e.g. The activation energy will fall because the ionisation energies of the metals fall. 2Mg + O 2MgO Mg will also react with warm water, giving a different magnesium hydroxide product. All group 2 elements except barium react directly with oxygen to form the simple oxide MO. There is an increase in the tendency to form the peroxide as you go down the Group. The equations for the reactions: You will need to use the BACK BUTTON on your browser to come back here afterwards. Group 2 elements (beryllium, magnesium, calcium, strontium and barium) react oxygen. It would be quite untrue to say that they burn more vigorously as you go down the Group. But how reactive a metal seems to be depends on how fast the reaction happens - not the overall amount of heat evolved. reactivity trend down group 2 with water. If this is the first set of questions you have done, please read the introductory page before you start. Mg + 2 H2O Mg(OH) 2 + H2 This is a much slower reaction than the reaction with steam and there is no flame. Question: (a) Write Chemical Equations For The Reactions Of Oxygen With Group 1 Metals And Group 2 Metals Respectiv (4 Marks) (b) Discuss The Trend Of Thermal Stability Of Group 1 And Group 2 Peroxides. Their ions only carry one positive charge, and so the lattice energies of their nitrides will be much less. Nitrogen is often thought of as being fairly unreactive, and yet all these metals combine with it to produce nitrides, X3N2, containing X2+ and N3- ions. As a whole, metals when burns with the oxygen form a simple metal oxide. This energy has to be recovered from somewhere to give an overall exothermic reaction - if the energy can't be recovered, the overall change will be endothermic and will not happen. In each case, you will get a mixture of the metal oxide and the metal nitride. Discusses trends in atomic radius, ionisation energy, electronegativity and melting point of the Group 2 elements. It is easier for group 2 elements to lose 2 electrons the further away the electrons are from the nucleus ( as you go down there are more shells), hence the trend is as you go down the group 2 elements the reactivity with oxygen increases. The peroxide ion, O22- looks like this: The covalent bond between the two oxygen atoms is relatively weak. Now imagine bringing a small 2+ ion close to the peroxide ion. In this video I take a look at some of the different ways in which group 2 elements can react. The reactions of the Group 2 metals with air rather than oxygen is complicated by the fact that they all react with nitrogen to produce nitrides. . It would be tempting to say that the reactions get more vigorous as you go down the Group, but it isn't true. PERIODIC TABLE GROUP 2 MENU . A/AS level. It would be quite untrue to say that they burn more vigorously as you go down the Group. In this case, though, the effect of the fall in the activation energy is masked by other factors - for example, the presence of existing oxide layers on the metals, and the impossibility of controlling precisely how much heat you are supplying to the metal in order to get it to start burning. information contact us at info@libretexts.org, status page at https://status.libretexts.org. Only in lithium's case is enough energy released to compensate for the energy needed to ionize the metal and the nitrogen - and so produce an exothermic reaction overall. The reaction of Group II Elements with Oxygen. (b) Relative Reactivities of the Group 2 elements Mg → Ba shown by their redox reactions with: (i) Oxygen (ii) Water (iii) Dilute acids {Reactions with acids will be limited to those producing a salt and Hydrogen.} The strontium equation would look just the same. Mg ribbon will often have a thin layer of magnesium oxide on it formed by reaction with oxygen. A reducing agent is the compound that gets oxidised in the reaction and, therefore, loses electrons. Reaction with halogens. This page looks at the reactions of the Group 2 elements - beryllium, magnesium, calcium, strontium and barium - with air or oxygen. 2Mg + O2 2MgO This needs to be cleaned off by emery paper before doing reactions with Mg ribbon. 2M(s) + O Barium: I have also only seen this burn on video, and although the accompanying description talked about a pale green flame, the flame appeared to be white with some pale green tinges. Reactions with oxygen … When something like magnesium nitride forms, you have to supply all the energy needed to form the magnesium ions as well as breaking the nitrogen-nitrogen bonds and then forming N3- ions. Barium forms barium peroxide (BaO 2) because the larger O 2 2− ion is better able to separate the large Ba 2+ ions in the crystal lattice. For example, Barium peroxide can form because the barium ion is so large that it doesn't have such a devastating effect on the peroxide ions as the metals further up the Group. Electrons in the peroxide ion will be strongly attracted towards the positive ion. The reactions of the Group 2 metals with air rather than oxygen is complicated by the fact that they all react with nitrogen to produce nitrides. All Group 2 elements tarnish in air to form a coating of the metal oxide. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. The reactions of the Group 2 metals with air rather than oxygen is complicated by the fact that they all react with nitrogen to produce nitrides. But how reactive a metal seems to be depends on how fast the reaction happens (i.e., Kinetics) - not the overall amount of heat evolved (i.e., Thermodynamics). Lithium has by far the smallest ion in the Group, and so lithium nitride has the largest lattice energy of any possible Group 1 nitride. This is in contrast to what happens in Group 1 of the Periodic Table (lithium, sodium, potassium, rubidium and cesium). The size of the lattice energy depends on the attractions between the ions. REACTIONS OF THE GROUP 2 ELEMENTS WITH AIR OR OXYGEN. 2:09 know the approximate percentages by volume of the four most abundant gases in dry air Exposed to air, it will absorb water vapour from the air, forming a solution. This Module addressed why it is difficult to observe a tidy pattern of this reactivity. In this case, though, the effect of the fall in the activation energy is masked by other factors - for example, the presence of existing oxide layers on the metals, and the impossibility of controlling precisely how much heat you are supplying to the metal in order to get it to start burning. Reactions with water . We say that the positive ion polarises the negative ion. All group 2 elements want to lose 2 electrons and all group 6 elements (oxygen) want to gain 2 electrons. Reaction of Group-2 Metals with Cl 2 : All Gr-2 metals except Be react with chlorine to give ionic chlorides whereas Be reacts with chlorine to give covalent chloride . We say that the positive ion polarizes the negative ion. strontium and water reaction. The lattice energy is greatest if the ions are small and highly charged - the ions will be close together with very strong attractions. At room temperature, oxygen reacts with the surface of the metal. For example, Magnesium reacts with Oxygen to form Magnesium Oxide the formula for which is: 2Mg (s) + O 2 (g) 2MgO (s) This is a redox reaction. The alkali metals react with oxygen. The Facts. What the metals look like when they burn is a bit problematical! It is then so hot that it produces the typical intense white flame. The overall amount of heat evolved when one mole of oxide is produced from the metal and oxygen also shows no simple pattern: If anything, there is a slight tendency for the amount of heat evolved to decrease as you go down the Group. This energy is known as lattice energy or lattice enthalpy. Mixtures of barium oxide and barium peroxide will be produced. A high charge density simply means that you have a lot of charge packed into a small volume. There is an increase in the tendency to form the peroxide as you go down the Group. The reactions of the alkaline earth metals with oxygen are less complex than those of the alkali metals. "X" in the equation can represent any of the metals in the Group. to generate metal oxides. This energy has to be recovered from somewhere to give an overall exothermic reaction - if the energy can't be recovered, the overall change will be endothermic and won't happen. Unit AS 2: Further Physical and inorganic Chemistry and an Introdution to Organic Chemistry. Ca(s) + H2O(l) → Ca(OH)2(aq) + H2(g) The general formula for this reaction is MO (where M is the group 2 element). The speed is controlled by factors like the presence of surface coatings on the metal and the size of the activation energy. It explains why it is difficult to observe many tidy patterns. Reactions with dilute hydrochloric acid All the metals react with dilute hydrochloric acid to give bubbles of hydrogen and a colourless solution of the metal chloride. Lithium has by far the smallest ion in the Group, and so lithium nitride has the largest lattice energy of any possible Group 1 nitride. Energy is evolved when the ions come together to produce the crystal lattice (lattice energy or enthalpy). It can't be done! When the crystal lattices form, so much energy is released that it more than compensates for the energy needed to produce the various ions in the first place. There are also problems with surface coatings. REACTIONS OF THE GROUP 2 ELEMENTS WITH AIR OR OXYGEN This page looks at the reactions of the Group 2 elements - beryllium, magnesium, calcium, strontium and barium - with air or oxygen. The excess energy evolved makes the overall process exothermic. Group 2 have 2 outer electrons which are less easily lost compared to group 1 At the top of group 2 ionisation energies are often too high for the electrons to be removed so they're relatively unreactive, reactivity increases down group 2 also. e.g. Legal. This property is known as deliquescence. questions on the reactions of Group 2 elements with air or oxygen, © Jim Clark 2002 (last modified February 2015), reactions of these metals with water (or steam). The Facts The reactions with oxygen Formation of simple oxides This is then well on the way to forming a simple oxide ion if the right-hand oxygen atom (as drawn below) breaks off. In the whole of Group 2, the attractions between the 2+ metal ions and the 3- nitride ions are big enough to produce very high lattice energies. This works best if the positive ion is small and highly charged - if it has a high charge density. The reactions with oxygen. 1.3.2 (a) Redox Reactions of Group 2 Metals. The Reactions with Air. You might possibly be able to imagine a trace of very pale greenish colour surrounding the white flame in the third video, but to my eye, they all count as a white flame. This is because the less electronegative sodium has a weak Na-O bond and the oxygen is more easily given up to react with H+. Looks at the trends in the reactions between the Group 2 elements and water. The familiar white ash you get when you burn magnesium ribbon in air is a mixture of magnesium oxide and magnesium nitride (despite what you might have been told when you were first learning Chemistry!). Water: Barium peroxide can form because the barium ion is so large that it doesn't have such a devastating effect on the peroxide ions as the metals further up the Group. Why do some metals form peroxides on heating in oxygen? The size of the lattice energy depends on the attractions between the ions. The general equation for the Group is: \[ 3X_{(s)} + N_{2(g)} \rightarrow X_3N_{2(s)}\]. Reactions with oxygen. Reactions. Beryllium has a very strong (but very thin) layer of beryllium oxide on its surface, and this prevents any new oxygen getting at the underlying beryllium to react with it. a) Virtually no reaction occurs between magnesium and cold water. To be able to make any sensible comparison, you would have to have pieces of metal which were all equally free of oxide coating, with exactly the same surface area and shape, exactly the same flow of oxygen around them, and heated to exactly the same extent to get them started. 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