Difference between Metals and Non-Metals
Substances can be categorized by comparing their physical and chemical properties.
Anodizing - It 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.
Clean Aluminum is made the anode and is electrolyzed with dilute H2SO4 The oxide layer can be dyed to give attractive finish to Aluminum.
What is Aqua-Regia (Royal Water) ?
Conc HCl (3 Parts) + Conc. HNO3 (1 Part)
It can even dissolve gold and platinum. It is a highly corrosive and fuming liquid.
Metals + Water
Metal + Water → Metal oxide + Hydrogen
Metal oxide + Water → Metal hydroxide
Metals react with water to produce metal oxide. The metal oxide produced further reacts with water to produce metal hydroxide.
Some metals react vigorously with cold water and produce hydrogen gas which burns instantaneously because of the heat produced in the reaction. Such a reaction is exothermic.
2K(s) + 2H2O(l) → 2KOH(aq) + H2(g) + heat energy
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g) + heat energy
The reaction of calcium with water is less violent and the heat released is not sufficient for hydrogen to catch fire. But calcium starts floating because of bubbles of hydrogen.
Magnesium does not react with cold water. It reacts with hot water.
Aluminium, Iron and Zinc do not react with hot water, They react with steam.
Metals such as lead, copper, silver and gold do not react with water at all.
Metals + Solution of Metal Salts
- Reactive metals can displace less reactive metals from their compounds in solution or molten form. All metals are not equally reactive. If a metal A displaces another metal B from its salt solution then A is more reactive than B.
Metal A + Salt solution of B → Salt solution of A + Metal B
This is a Displacement Reaction
Metals + Non Metals
Metals and Non-Metals react to achieve octet configuration and form an ionic bond. Metals lose electrons to form positive ions which are gained by non-metals to form negative ions.
These ions being oppositely charged combine together to form a salt due to presence of strong electrostatic force.
The compounds formed in this manner by the transfer of electrons from a metal to a non-metal are known as ionic compounds or electrovalent compounds.
Properties of Ionic Compounds
1. They are solids - Because of strong electrostatic force.
2. They are generally brittle - Can break easily with little pressure.
3. They have high melting and boiling points.
4. They are generally soluble in water and insoluble in solvents such as kerosene, petrol etc.
5. They are generally good conductors of electricity due to presence of ions.
Occurrence of Metals
The elements or compounds, which occur naturally in the earth’s crust, are known as minerals. At some places, minerals contain a very high percentage of a particular metal and the metal can be profitably extracted from it. These minerals are called ores.
Most metals are found in the earths crust. Sea water also has some metals due to presence of salts such as NaCl, MgCl2.
Some metals are found in free state. Some are found in form of compounds.
Metals low in reactivity series do not react and are hence found in free states and those with higher reactivity are found in form of compounds.
Gold, Silver, Platinum and Copper are found in the free state.
Copper and silver are also found in the combined state as their sulphide or oxide ores.
The metals at the top of the activity series (K, Na, Ca, Mg and Al) are so reactive that they are never found in nature as free elements.
The metals in the middle of the activity series (Zn, Fe, Pb, etc.) are moderately reactive. They are found in the earth’s crust mainly as oxides, sulphides or carbonates.
Thus on the basis of reactivity, we can group the metals into the following three categories
(i) Metals of low reactivity;
(ii) Metals of medium reactivity;
(iii) Metals of high reactivity.
Different techniques are to be used for obtaining the metals falling in each category.