The speed is controlled by factors like the presence of surface coatings on the metal and the size of the activation energy. In this video I take a look at some of the different ways in which group 2 elements can react. REACTIONS OF THE GROUP 2 ELEMENTS WITH AIR OR OXYGEN. Electrons in the peroxide ion will be strongly attracted towards the positive ion. The group 2 metals (M (s)) react with oxygen gas (O 2(g)) at room temperature and pressure to form oxides with the general formula MO as shown in the balanced chemical reactions below: 2Be (s) O 2(g) Water: Only in lithium's case is enough energy released to compensate for the energy needed to ionise the metal and the nitrogen - and so produce an exothermic reaction overall. "X" in the equation can represent any of the metals in the Group. It explains why it is difficult to observe many tidy patterns. Mg burns with a bright white flame. Reactions with water . Calcium is quite reluctant to start burning, but then bursts dramatically into flame, burning with an intense white flame with a tinge of red at the end. The general equation for the Group is: $3X_{(s)} + N_{2(g)} \rightarrow X_3N_{2(s)}$. You will notice that the trend in the pH of the solutions formed goes from alkaline to acidic. Trying to pick out patterns in the way the metals burn. Group 2 reactions Reactivity of group 2 metals increases down the group Mg will also react slowly with oxygen without a flame. PERIODIC TABLE GROUP 2 MENU . Lithium is the only metal in Group 1 to form a nitride. 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. (3 Marks) (d) Heating Group 2 Carbonates, Such As CaCO3 Leads To Decomposition. But how reactive a metal seems to be depends on how fast the reaction happens - not the overall amount of heat evolved. 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. The size of the lattice energy depends on the attractions between the ions. Magnesium, on the other hand, has to be heated to quite a high temperature before it will start to react. Legal. 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. They react violently in pure oxygen producing a white ionic oxide. in the air. 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. While it would be tempting to say that the reactions get more vigorous as you go down the Group, but it is not true. Why do some metals form peroxides on heating in oxygen? Once started, the reactions with Oxygen and Chlorine are vigorous: 2Mg(s) + O 2 (g) è2MgO(s) Ca(s) + Cl 2 (g) è CaCl 2 (s) All the metals except Beryllium form oxides in air at room temperature which dulls the surface of the metal. This energy is known as lattice energy or lattice enthalpy. Their ions only carry one positive charge, and so the lattice energies of their nitrides will be much less. 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. 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. We say that the positive ion polarises the negative ion. 2.11.3 investigate and describe the reactions of the elements with oxygen, water and dilute acids; 2Mg + O 2MgO Mg will also react with warm water, giving a different magnesium hydroxide product. Reactions with oxygen … Mg ribbon will often have a thin layer of magnesium oxide on it formed by reaction with oxygen. On the whole, the metals burn in oxygen to form a simple metal oxide. The lattice energy is greatest if the ions are small and highly charged - the ions will be close together with very strong attractions. 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. On the whole, the metals burn in oxygen to form a simple metal oxide. Group 2 reactions Reactivity of group 2 metals increases down the group Mg will also react slowly with oxygen without a flame. There are also problems with surface coatings. It reacts with cold water to produce an alkaline solution of calcium hydroxide and hydrogen gas is released. The strontium equation would look just the same. This page looks at the reactions of the Group 2 elements - beryllium, magnesium, calcium, strontium and barium - with air or oxygen. A high charge density simply means that you have a lot of charge packed into a small volume. This leads to lower activation energies, and therefore faster reactions. strontium and water reaction. Mg + 2 H2O Mg(OH) 2 + H2 This is a much slower reaction than the reaction with steam and there is no flame. Strontium and barium will also react with oxygen to form strontium or barium peroxide. In each case, you will get a mixture of the metal oxide and the metal nitride. The excess energy evolved makes the overall process exothermic. The equations for the reactions: For example, the familiar white ash you get when you burn magnesium ribbon in air is a mixture of magnesium oxide and magnesium nitride. Why do these metals form nitrides on heating in air? This works best if the positive ion is small and highly charged - if it has a high charge density. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. This is compared to non-metals when the reactivity decreases working down a non-metal group such as group 7. Anhydrous calcium chloride is a hygroscopic substance that is used as a desiccant. Strontium: I have only seen this burn on video. To find the trend of reactions of metals with oxygen is almost impossible. All group 2 elements want to lose 2 electrons and all group 6 elements (oxygen) want to gain 2 electrons. Reactions. You haven't had to heat them by the same amount to get the reactions happening. a) Virtually no reaction occurs between magnesium and cold water. The activation energy will fall because the ionisation energies of the metals fall. The group 1 elements react with oxygen from the air to make metal oxides. 2.11 Group II elements and their compounds. There is an increase in the tendency to form the peroxide as you go down the Group. This is clearly seen if we observe the reactions of magnesium and calcium in water. At room temperature, oxygen reacts with the surface of the metal. . What the metals look like when they burn is a bit problematical! (a) describe the redox reactions of the Group 2 elements Mg to Ba: (i) with oxygen, (ii) with water; (b) explain the trend in reactivity of Group 2 elements down the group due to the increasing ease of forming cations, in terms of atomic size, shielding and nuclear attraction; Reactions of Group 2 compounds Group 2 elements (beryllium, magnesium, calcium, strontium and barium) react oxygen. The alkali metals react with oxygen. Describe the trend in the reactivity of group 2 elements with chlorine as you descend down the group. increases down the group because it becomes more easy to lose the two electrons. CaO(s) + H2O(l) ——> Ca(OH)2(s) Hydroxides • basic strength also increases down group • this is because the solubility increases • the metal ions get larger so charge density decreases • there is a lower attraction between the OH¯ ions and larger dipositive ions Energy is evolved when the ions come together to produce the crystal lattice. 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. A reducing agent is the compound that gets oxidised in the reaction and, therefore, loses electrons. In each case, you will get a mixture of the metal oxide and the metal nitride. 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. 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. Ca(s) + H2O(l) → Ca(OH)2(aq) + H2(g) It would obviously be totally misleading to say that magnesium is more reactive than potassium on the evidence of the bright flame. $2Mg_{(s)} + O_{2(g)} \rightarrow 2MgO_{(s)}$, $3Mg_{(s)} + N_{2(g)} \rightarrow Mg_3N_{2(s)}$. 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. This forms a white oxide, which covers the surface. 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. 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. Looks at the trends in the reactions between the Group 2 elements and water. 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. information contact us at info@libretexts.org, status page at https://status.libretexts.org. It is almost impossible to find any trend in the way the metals react with oxygen. 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 reaction of Group II Elements with Oxygen. $Ba_{(s)} + O_{2(s)} \rightarrow BaO_{2(s)}$. . 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. $2X_{(s)} + O_{2(g)} \rightarrow 2XO_{(s)}$. 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+. A/AS level. Strontium forms this if it is heated in oxygen under high pressures, but barium forms barium peroxide just on normal heating in oxygen. 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. 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 Module addressed why it is difficult to observe a tidy pattern of this reactivity. (i) The Reactions of Group 2 Elements with Oxygen. However, in a reaction with steam it forms magnesium oxide and hydrogen. The general formula for this reaction is MO (where M is the group 2 element). Reactivity increases down the group. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. For more information contact us at info@libretexts.org or check out our status page at https://status.libretexts.org. Formation of simple oxides. Strontium forms this if it is heated in oxygen under high pressures, but barium forms barium peroxide just on normal heating in oxygen. All group 2 elements except barium react directly with oxygen to form the simple oxide MO. Watch the recordings here on Youtube! CCEA Chemistry. 1.3.2 (a) Redox Reactions of Group 2 Metals. Those reactions don't happen, and the nitrides of sodium and the rest aren't formed. The group 2 metals will burn in oxygen. This is in contrast to what happens in Group 1 of the Periodic Table (lithium, sodium, potassium, rubidium and caesium). Those reactions don't happen, and the nitrides of sodium and the rest are not formed. Why do these metals form nitrides on heating in air? reactivity trend down group 2 with water. All of these processes absorb energy. 2Mg + O2 2MgO This needs to be cleaned off by emery paper before doing reactions with Mg ribbon. It cannot be said that by moving down the group these metals burn more vigorously. We say that the positive ion polarizes the negative ion. There are no simple patterns in the way the metals burn. (h) trend in general reactivity of Group 1 and Group 2 metals; Northern Ireland. 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. Reaction with water Most Group II oxides react with water to produce the hydroxide e.g. 2:09 know the approximate percentages by volume of the four most abundant gases in dry air As group 2 in the periodic table comprises of metals, the reactivity of group 2 elements towards chlorine increases when working our way down the group 2 metals. The has been reduced from 0 to -2. Unit AS 2: Further Physical and inorganic Chemistry and an Introdution to Organic Chemistry. M = Mg, Ca, Sr,Ba --> I will be using 'M' as the general symbol for a Group II element in this topic. The Facts The reactions with oxygen Formation of simple oxides 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. In all the other cases in Group 1, the overall reaction would be endothermic. The Group II elements are powerful reducing agents. 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. to generate metal oxides. It explains why it is difficult to observe many tidy patterns. Nitrogen is fairly unreactive because of the very large amount of energy is required to break the triple bond joining the two atoms in the nitrogen molecule, N2. MgO + 2HCl MgCl 2 + H 2O Reactions with oxygen. There are no simple patterns. You could argue that the activation energy will fall as you go down the Group and that will make the reaction go faster. Beryllium is reluctant to burn unless it is in the form of dust or powder. Exposed to air, it will absorb water vapour from the air, forming a solution. The speed is controlled by factors like the presence of surface coatings on the metal and the size of the activation energy. When these metals (M) are heated in oxygen they burn vigorously to produce a white ionic oxide, M2+O2-. Beryllium, magnesium and calcium don't form peroxides when heated in oxygen, but strontium and barium do. Magnesium, of course, burns with a typical intense white flame. 2Li(s) + Cl 2 (g) → 2LiCl(s) A similar reaction takes place with the other elements of group 7. In all the other Group 1 elements, the overall reaction would be endothermic. 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