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Hydrocarbons A compound made up of hydrogen and carbon only is called hydrocarbon (hydrogen   +   carbon = hydrocarbon ). Example of hydrocarbons are Methane (CH4), Ethane (C2H6), Ethene (C2H4), ethyne (C2H2).

Definition: the periodic table is a chart of elements prepared in such a way that the elements having similar properties of occur in the same vertical column or group. The horizontal rows of periodic table called periods. The vertical columns of the periodic table called groups.

Definition of Dobereiner's theory law in English and Hindi When elements are arranged in the order of increasing atomic masses, groups of 3 elements (known as triads), having similar properties are obtained. The atomic mass of the middle element of the triad being equal to the Arithmetic mean of the atomic masses of the other two elements.

Acids, Bases and Salts :  On basis of chemical properties compound are divided into three groups i) acids ii) bases and iii) salts. Here we discussed about Acids. What is Acid? An acid is a chemical substance which when dissolved in water yields hydrogen ions (or hydronium ions) as the only positively charged ions.

 Acids Bases and Salts Class 10 CBSE What is a salt? A salt is a compound formed by the replacement of hydrogen ions of an acid, partly or wholly by a metal or ammonium ion. Example sodium chloride, calcium sulphate etc. Again salts is formed by acid base neutralisation reaction. Such as sodium chloride (Nacl) is formed due to neutralisation reaction between sodium hydroxide (NaOH) and hydrochloric acid (Hcl).