Class X science chemistry 200 most important question series for PYQ cbse board exam 2023 ncert

Elements are classified on the basis of similarities in their properties. n Döbereiner grouped the elements into triads and Newlands gave the Law of Octaves. n Mendeléev arranged the elements in increasing order of their atomic masses and according to their chemical properties. n Mendeléev even predicted the existence of some yet to be discovered elements on the basis of gaps in his Periodic Table. n Anomalies in arrangement of elements based on increasing atomic mass could be removed when the elements were arranged in order of increasing atomic number, a fundamental property of the element discovered by Moseley. n Elements in the Modern Periodic Table are arranged in 18 vertical columns called groups and 7 horizontal rows called periods. n Elements thus arranged show periodicity of properties including atomic size, valency or combining capacity and metallic and non-metallic character. Carbon is a versatile element that forms the basis for all living organisms and many of the things we use. n This large variety of compounds is formed by carbon because of its tetravalency and the property of catenation that it exhibits. n Covalent bonds are formed by the sharing of electrons between two atoms so that both can achieve a completely filled outermost shell. n Carbon forms covalent bonds with itself and other elements such as hydrogen, oxygen, sulphur, nitrogen and chlorine. n Carbon also forms compounds containing double and triple bonds between carbon atoms. These carbon chains may be in the form of straight chains, branched chains or rings. n The ability of carbon to form chains gives rise to a homologous series of compounds in which the same functional group is attached to carbon chains of different lengths. n The functional groups such as alcohols, aldehydes, ketones and carboxylic acids bestow characteristic properties to the carbon compounds that contain them. n Carbon and its compounds are some of our major sources of fuels. n Ethanol and ethanoic acid are carbon compounds of importance in our daily lives. n The action of soaps and detergents is based on the presence of both hydrophobic and hydrophilic groups in the molecule and this helps to emulsify the oily dirt and hence its removal. Elements can be classified as metals and non-metals. n Metals are lustrous, malleable, ductile and are good conductors of heat and electricity. They are solids at room temperature, except mercury which is a liquid. n Metals can form positive ions by losing electrons to non-metals. n Metals combine with oxygen to form basic oxides. Aluminium oxide and zinc oxide show the properties of both basic as well as acidic oxides. These oxides are known as amphoteric oxides. n Different metals have different reactivities with water and dilute acids. n A list of common metals arranged in order of their decreasing reactivity is known as an activity series. n Metals above hydrogen in the Activity series can displace hydrogen from dilute acids. n A more reactive metal displaces a less reactive metal from its salt solution. n Metals occur in nature as free elements or in the form of their compounds. n The extraction of metals from their ores and then refining them for use is known as metallurgy. n An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal. n The surface of some metals, such as iron, is corroded when they are exposed to moist air for a long period of time. This phenomenon is known as corrosion. n Non-metals have properties opposite to that of metals. They are neither malleable nor ductile. They are bad conductors of heat and electricity, except for graphite, which conducts electricity. PDF प्राप्त करने के लिए आप हमारा टेलीग्राम चैनल ज्वाइन कर सकते हैं Our telegram link https://t.me/nbddevraj TARGET BOARD 2023 PLAYLISTS: CLASS 12 PHYSICS 1. Electric charge and field - https://youtube.com/playlist?list=PLaD6vjvzSDN1i-oUyajmQY4e8DZqcMx6I CHEMISTRY 1. Solution - https://youtube.com/playlist?list=PLaD6vjvzSDN0jos34GuRbd16xOkVX9BM6 IUPAC Nomenclature - https://youtube.com/playlist?list=PLaD6vjvzSDN3cX7l2_ffepfhl-QTBh-J- HALOALKANE - https://youtube.com/playlist?list=PLaD6vjvzSDN1Y783GYexyhoWa1y0OFKEh OUR SOCIAL MEDIA LINKS : FACEBOOK - https://www.facebook.com/profile.php?id=100071572310349 INSTAGRAM - https://instagram.com/divyachem_?igshid=YmMyMTA2M2Y= FACEBOOK PAGE - https://www.facebook.com/Divyachem-100324816101067/

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