Chemistry Class 9 Chapter 8 Notes
Important Notes of Chemistry Class 9 Chapter 8 Notes Urdu Medium written by Honorable Sir M. Shahid Suib. These notes are very helpful in the preparation of Chemical Reactivity Class 9 Notes for students of the Chemistry Class 9 Chapter 8 Notes Urdu Medium and these are according to the paper patterns of all Punjab boards.
Summary and Contents:
Topics which are discussed in the notes are given below:
- Here are the detailed 9th class chemistry chapter 8 notes to help you prepare for your exams.
- Complete Exercise MCQs of Chapter No.8: Chemical Reactivity in Urdu Medium
- Complete Exercise Short Questions with Answers of Chapter No.8: Chemical Reactivity in Urdu Medium
- Major Concepts: 1. Metal 2. Non-Metals
- The different kinds of materials around us exist in variety of forms. Things like aeroplanes, trains, building frames, automobiles or even different machines and tools, are due to different properties of various metals. The non-metals exist as gases, liquids and soft or hard solids. They occupy upper right positions in the Periodic Table. Carbon, nitrogen, phosphorus, oxygen, sulphur, most of the halogens and the noble gases are non-metals. They show a variety of chemical reactivities. They form different ionic and covalent compounds, many of which are solids or gases.
- METALS: Metals are the elements (except hydrogen) which are electropositive and form cations by losing electrons. Metals can be categorized.
- Very reactive: potassium, sodium, calcium, magnesium and aluminium.
- Moderately reactive: zinc, iron, tin and lead.
- Least reactive or noble: copper, mercury, silver and gold.
- Some common metals and non-metals in the periodic table.
- Important physical characteristics of metals are listed below:
- Almost all metals are solids (except mercury)
- Almost all metals are solids (except mercury)
- They have high melting and boiling points, (except alkali metals)
- They possess metallic luster and can be polished.
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- They are malleable (can be hammered into sheets), ductile (can be drawn into wires) and give off a tone when hit.
- They are good conductor of heat and electricity.
- They have high densities.
- They are hard (except sodium and potassium).
- Important chemical properties of metals are:
- They easily lose electrons and form positive ions.
- They readily react with oxygen to form basic oxides.
- They usually form ionic compounds with non-metals.
- They have metallic bonding.
- Electropositive Character Class 9: Metals have the tendency to lose their valance electrons. This property of a metal is termed as electropositivity or metallic character. The more easily a metal loses its electrons, the more electropositive it is. The number of electrons lost by an atom of a metal is called its valency.
- Trends of electropositivity: Electropositive character increases down the group because size of atoms increases. For example, lithium metal is less electropositive than sodium which is in turn less electropositive than potassium.
- Electropositivity and ionization energy: Electropositive character depends upon the ionization energy which in turn depends upon size and nuclear charge of the atom. Small sized atoms with high nuclear charge have high ionization energy value. In this way, atoms having high ionization energy are less electropositive or metallic.
- Uses of sodium class 9: Sodium-potassium alloy is used as a coolant in nuclear reactors. It is used as a reducing agent in the extraction of metals like Ti. It is used to produce yellow light in sodium vapour lamps.
- Uses of magnesium class 9: Magnesium is used in flash light bulbs and in fireworks. Magnesium ribbon is used in Thermite process to ignite aluminium powder. Magnesium is used as anode for prevention of corrosion. It is used in the manufacture of light alloys.
- Uses of calcium: It is used to remove sulphur from petroleum products. It is used as reducing agent to produce Cr, U and Zr.
- Inertness of Noble Metals class 9: The elements in which d-orbital are in the process of filling, constitute a group of metals called transition metals or d-group elements. They exhibit a variety of oxidation states.
- Gold is a yellow soft metal. It is most malleable and ductile of all the metals. One gram of gold can be drawn into a wire of one and a half kilometre long. Gold is very non-reactive or inert metal. It is not affected by atmosphere. It is not even affected by any single mineral acid or base.
- NON-METALS: Non-metals form negative ions (anions) by gaining electrons. In this way, non-metals are electronegative in nature and form acidic oxides. The valency of some non-metals depend upon the number of electrons accepted by them. For example, valency of chlorine atom is 1, as it accepts only 1 electron in its outermost shell.
- Important physical properties of non-metals class9:
- Physical properties of non-metals change gradually but uniquely in a group of non-metals. Non-metals usually exist in all three physical states of matter. The non-metals at the top of the group are usually gases while others are either liquids or solids.
- Solids non-metals are brittle (break easily).
- Non-metals are bad conductors of heat and electricity (except graphite).
- They are not shiny, they are dull except iodine (it is lustrous like metals).
- They are generally soft (except diamond).
- They have low melting and boiling points (except silicon, graphite and diamond).
- They have low densities.
- Important chemical properties of non-metals:
- Non-metals usually do not react with water.
- They do not react with dilute acids because non-metals are itself electron acceptors.
- Their valence shells are deficient of electrons, therefore, they readily accept electrons to complete their valence shells and become stable.
- Important MCQs and Questions of Chemical Reactivity: