Metals and Nonmetals for (2009-2010)

Reactivity series The series of metals in which they are arranged in order of their decreasing reactivity is called reactivity of activity series.

Reactivity The tendency of an element to attain a completely filled outermost shell by losing or gaining electrons is called reactivity.

Ionic compounds The compounds formed by losing or gaining electrons or by the transfer of electrons from metal to nonmetal are called ionic compounds or electrovalent compounds. Ionic bonds are formed between metals and nonmetals. E.g. NaCl, MgO, CaCl₂, NaOH, Al₂O₃, etc.

Properties of ionic compounds

1. Ionic compounds are solids and hard because of strong force of attraction between positive and negative ions. They are brittle.
2. Melting and boiling points of ionic compounds are high because a large amount of energy is required to break the inter-ionic attraction.
3. Solution of ionic compound in water contains ions which move towards oppositely charged electrodes when electricity is passed. This is why ionic compounds are very good conductors of electricity.
4. Ionic compounds in a solid state do not conduct electricity because movement of ions in solid state is not possible due to rigid structure. So they conduct electricity only in molten state.

Covalent compounds The compounds formed by sharing of electrons between nonmetals are called covalent compounds. Covalent bonds are formed between nonmetals. E.g. HCl, H₂O, NH₃, CH₄, CO₂, SO₂, N₂, O₂, etc.

Properties of covalent compounds

1. The covalent compounds are usually liquids due to the weak forces of attraction between their molecules.
2. They usually have low melting and boiling points because the force of attraction between molecules is very weak and a small amount of energy is required to break these forces.
3. They do not conduct electricity because they do not contain ions in molten state.
4. They are usually insoluble in water because they form covalent compounds.

Minerals The elements and compounds which are found naturally in the earth crust are called minerals.

Ores The minerals from which metals can be extracted easily and profitably are called ores. An ore contains good percentage of metals and less impurities.

All ores are minerals but all minerals are not ores because there may be some minerals from which metals cannot be extracted easily and profitably.
Gangue The unwanted materials or the impurities like soil and sand present in an ore are called gangue.

Extraction of metals There are three main steps that are used in the extraction of metals. They are

1. Enrichment or concentration of ore.
2. Conversion of ore into metal (reduction).
3. Refining of metals.

Enrichment of ore The process of removing impurities from an ore is called enrichment of ore. The methods used for removing impurities from ore are based on the differences in the physical and chemical properties of the ore and gangue

Nature of elements in the bottom of reactivity series The metals in the bottom of reactivity series are least reactive or unreactive, so they are found in free-state.

E.g. gold, platinum, and copper.