Class 10 Chemical properties of metals, Reactivity series, How do metals and non-metals react, Properties of ionic compounds

### Topics to be covered

=> Chemical properties of metals
=> Reactivity series
=> How do metals and non-metals react
=> Properties of ionic compounds

### 𝐂𝐇𝐄𝐌𝐈𝐂𝐀𝐋 𝐏𝐑𝐎𝐏𝐄𝐑𝐓𝐈𝐄𝐒 𝐎𝐅 𝐌𝐄𝐓𝐀𝐋𝐒

color{green}("𝟏 𝐑𝐄𝐀𝐂𝐓𝐈𝐎𝐍 𝐖𝐈𝐓𝐇 𝐎𝐗𝐘𝐆𝐄𝐍 :")

color{green}(★) Almost all metals combine with oxygen to form metal oxides.

color{red}("𝐌𝐞𝐭𝐚𝐥 + 𝐎𝐱𝐲𝐠𝐞𝐧 → 𝐌𝐞𝐭𝐚𝐥 𝐎𝐱𝐢𝐝𝐞")

color{green}(•) For example, when copper is heated in air, it combines with oxygen to form copper(II) oxide, a black oxide.

color{red}(underset("(Copper)")(2Cu) + O_2 → underset("(Copper(II) oxide)")(2CuO))

color{green}(•) Aluminium forms aluminium oxide.

color{red}(underset("(Aluminium)")(4Al) + 3O_2 → underset("(Aluminium oxide)")(2Al_2O_3))

color{green}(★) Some metal oxides, such as aluminium oxide, zinc oxide, etc., show both acidic as well as basic behaviour. Such metal oxides which react with both acids as well as bases to produce salts and water are known as amphoteric oxides. For eg:

color{red}(Al_2O_3 + 6HCl → 2AlCl_3 + 3 H_2O)

color{red}(Al_2O_3 + NaOH → underset("(Sodium aluminate)")(2NaAlO_2) + H_2O)

color{green}(★) Most metal oxides are insoluble in water but some of these dissolve in water to form alkalis. Sodium oxide and potassium oxide dissolve in water to produce alkalis as follows –

color{red}(Na_2O(s) + H_2O(l) → 2NaOH (aq))

color{red}(K_2O(s) + H_2O(l) → 2KOH (aq))

color{green}(★) Different metals show different reactivities towards oxygen.

color{green}(•) Metals such as potassium and sodium react so vigorously that they catch fire if kept in the open. Hence, to protect them and to prevent accidental fires, they are kept immersed in kerosene oil.

color{green}(•) At ordinary temperature, the surfaces of metals such as magnesium, aluminium, zinc, lead, etc., are covered with a thin layer of oxide. The protective oxide layer prevents the metal from further oxidation.

color{green}(•) Iron does not burn on heating but iron filings burn vigorously when sprinkled in the flame of the burner.

color{green}(•) Copper does not burn, but the hot metal is coated with a black coloured layer of copper(II) oxide.

color{green}(•) Silver and gold do not react with oxygen even at high temperatures.

color{green}(•) Sodium is the most reactive of the samples of metals taken here.

color{green}(•) The reaction of magnesium is less vigorous implying that it is not as reactive as sodium.
But burning in oxygen does not help us to decide about the reactivity of zinc, iron, copper or lead.

color{red}(" 𝐉𝐔𝐒𝐓 𝐅𝐎𝐑 𝐂𝐔𝐑𝐈𝐎𝐔𝐒 ")

color{green}(★) Anodising is a process of forming a thick oxide layer of aluminium. Aluminium develops a thin oxide layer when exposed to air. This aluminium oxide coat makes it resistant to further corrosion. The resistance can be improved further by making the oxide layer thicker. During anodising, a clean aluminium article is made the anode and is electrolysed with dilute sulphuric acid. The oxygen gas evolved at the anode reacts with aluminium to make a thicker protective oxide layer. This oxide layer can be dyed easily to give aluminium articles an attractive finish.

color{green}("𝟐 𝐑𝐄𝐀𝐂𝐓𝐈𝐎𝐍 𝐖𝐈𝐓𝐇 𝐖𝐀𝐓𝐄𝐑 ")

color{green}(★) Metals upon reaction with water and produce a metal oxide and hydrogen gas. Metal oxides that are soluble in water dissolve in it to further form metal hydroxide. But all metals do not react with water.

color{red}(" 𝐌𝐞𝐭𝐚𝐥 + 𝐖𝐚𝐭𝐞𝐫 → 𝐌𝐞𝐭𝐚𝐥 𝐨𝐱𝐢𝐝𝐞 + 𝐇𝐲𝐝𝐫𝐨𝐠𝐞𝐧")

color{red}("𝐌𝐞𝐭𝐚𝐥𝐬 𝐨𝐱𝐢𝐝𝐞𝐬 + 𝐖𝐚𝐭𝐞𝐫 → 𝐌𝐞𝐭𝐚𝐥 𝐡𝐲𝐝𝐫𝐨𝐱𝐢𝐝𝐞 ")

color{green}(★) Metals like potassium and sodium react violently with cold water. In case of sodium and potassium, the reaction is so violent and exothermic that the evolved hydrogen immediately catches fire.

color{red}(2K(s) + 2H_2O (l) → 2KOH (aq) + H_2 (g) + " heat energy")

color{red}(2Na(s) + 2H_2O(l) → 2NaOH (aq) + H_2(g) + " heat energy ")

color{green}(★) The reaction of calcium with water is less violent. The heat evolved is not sufficient for the hydrogen to catch fire.

color{red}(Ca(s) + 2H_2O(l) → Ca(OH)_2 (aq) + H_2(g))

Calcium starts floating because the bubbles of hydrogen gas formed stick to the surface of the metal.

Magnesium does not react with cold water. It reacts with hot water to form magnesium hydroxide and hydrogen. It also starts floating due to the bubbles of hydrogen gas sticking to its surface.

color{green}(★) Metals like aluminium, iron and zinc do not react either with cold or hot water. But they react with steam to form the metal oxide and hydrogen.

color{red}(2Al(s) + 3 H_2O(g) → Al_2O_3 (s) + 3H_2 (g))

color{red}(3Fe(s) + 4 H_2O(g) → Fe_3O_4 (s) + 4 H_2(g))

Metals such as lead, copper, silver and gold do not react with water at all.

color{green}("𝟑 𝐑𝐄𝐀𝐂𝐓𝐈𝐎𝐍 𝐖𝐈𝐓𝐇 𝐀𝐂𝐈𝐃𝐒:")

color{green}(★) Metals react with acids to give a salt and hydrogen gas.

color{red}("𝐌𝐞𝐭𝐚𝐥 + 𝐃𝐢𝐥𝐮𝐭𝐞 𝐚𝐜𝐢𝐝 → 𝐒𝐚𝐥𝐭 + 𝐇𝐲𝐝𝐫𝐨𝐠𝐞𝐧 ")

color{green}(★) Hydrogen gas is not evolved when a metal reacts with nitric acid. It is because color{red}(HNO_3) is a strong oxidising agent. It oxidises the color{red}(H_2) produced to water and itself gets reduced to any of the nitrogen oxides color{red}((N_2O, NO, NO_2 )).

color{green}(★) But magnesium color{red}((Mg)) and manganese color{red}((Mn)) react with very dilute color{red}(HNO_3) to evolve color{red}(H_2) gas.

color{green}(★) The reactivity decreases in the order color{red}(Mg > Al > Zn > Fe). In the case of copper, no bubbles were seen and the temperature also remained unchanged. This shows that copper does not react with dilute color{red}(HCl).

color{red}(" 𝐉𝐔𝐒𝐓 𝐅𝐎𝐑 𝐂𝐔𝐑𝐈𝐎𝐔𝐒 ")

color{green}(★) Aqua regia, (Latin for ‘royal water’) is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1. It can dissolve gold, even though neither of these acids can do so alone. Aqua regia is a highly corrosive, fuming liquid. It is one of the few reagents that is able to dissolve gold and platinum.

color{green}("𝟒 𝐑𝐄𝐀𝐂𝐓𝐈𝐎𝐍 𝐖𝐈𝐓𝐇 𝐒𝐎𝐋𝐔𝐓𝐈𝐎𝐍𝐒 𝐎𝐅 𝐎𝐓𝐇𝐄𝐑 𝐌𝐄𝐓𝐀𝐋 𝐒𝐀𝐋𝐓𝐒:")

color{green}(★) Reactive metals can displace less reactive metals from their compounds in solution or molten form.

color{green}(★) Displacement reactions give better evidence about the reactivity of metals. It is simple and easy if metal A displaces metal B from its solution, it is more reactive than B.

color{red}("𝐌𝐞𝐭𝐚𝐥 𝐀 + 𝐒𝐚𝐥𝐭 𝐬𝐨𝐥𝐮𝐭𝐢𝐨𝐧 𝐨𝐟 𝐁 → 𝐒𝐚𝐥𝐭 𝐬𝐨𝐥𝐮𝐭𝐢𝐨𝐧 𝐨𝐟 𝐀 + 𝐌𝐞𝐭𝐚𝐥 𝐁 ")

### 𝐓𝐡𝐞 𝐑𝐞𝐚𝐜𝐭𝐢𝐯𝐢𝐭𝐲 𝐒𝐞𝐫𝐢𝐞𝐬

color{green}(★) A list of metals arranged in the order of their decreasing activities is called reactivity series.

### 𝐇𝐎𝐖 𝐃𝐎 𝐌𝐄𝐓𝐀𝐋𝐒 𝐀𝐍𝐃 𝐍𝐎𝐍-𝐌𝐄𝐓𝐀𝐋𝐒 𝐑𝐄𝐀𝐂𝐓

color{green}(★) The compounds formed by the transfer of electrons from a metal to a non-metal are known as ionic compounds or electrovalent compounds.

color{green}(★) Sodium and chloride ions, being oppositely charged, attract each other and are held by strong electrostatic forces of attraction to exist as sodium chloride (NaCl). It should be noted that sodium chloride does not exist as molecules but aggregates of oppositely charged ions.

### PROPERTIES OF IONIC COMPOUNDS

color{green}("(𝐢) 𝐏𝐡𝐲𝐬𝐢𝐜𝐚𝐥 𝐧𝐚𝐭𝐮𝐫𝐞:") Ionic compounds are solids and are somewhat hard because of the strong force of attraction between the positive and negative ions. These compounds are generally brittle and break into pieces when pressure is applied.

color{green}("(𝐢𝐢) 𝐌𝐞𝐥𝐭𝐢𝐧𝐠 𝐚𝐧𝐝 𝐁𝐨𝐢𝐥𝐢𝐧𝐠 𝐩𝐨𝐢𝐧𝐭𝐬:") Ionic compounds have high melting and boiling points . This is because a considerable amount of energy is required to break the strong inter-ionic. attraction.

color{green}("(𝐢𝐢𝐢) 𝐒𝐨𝐥𝐮𝐛𝐢𝐥𝐢𝐭𝐲 :") Electrovalent compounds are generally soluble in water and insoluble in solvents such as kerosene, petrol, etc.

color{green}("(𝐢𝐯) 𝐂𝐨𝐧𝐝𝐮𝐜𝐭𝐢𝐨𝐧 𝐨𝐟 𝐄𝐥𝐞𝐜𝐭𝐫𝐢𝐜𝐢𝐭𝐲 :") A solution conducts electricity when there occurs the movement of charged particles. A solution of an ionic compound in water contains ions, which move to the opposite electrodes when electricity is passed through the solution. 𝐈𝐨𝐧𝐢𝐜 𝐜𝐨𝐦𝐩𝐨𝐮𝐧𝐝𝐬 𝐢𝐧 𝐭𝐡𝐞 𝐬𝐨𝐥𝐢𝐝 𝐬𝐭𝐚𝐭𝐞 𝐝𝐨 𝐧𝐨𝐭 𝐜𝐨𝐧𝐝𝐮𝐜𝐭 𝐞𝐥𝐞𝐜𝐭𝐫𝐢𝐜𝐢𝐭𝐲 because movement of ions in the solid is not possible due to their rigid structure. But ionic compounds conduct electricity in the molten state. This is possible in the molten state since the elecrostatic forces of attraction between the oppositely charged ions are overcome due to the heat. Thus, the ions move freely and conduct electricity.