Make placards with symbols and valencies of the elements separately. Each student should hold two placards, one with the symbol in the right hand and the other with the valency in the left hand. Keeping the symbols in place, students should criss-cross their valencies to form the formula of a compound.

The students of class IX have made placards showing the symbols of some elements and valencies of these elements. These placards somehow got mixed up as shown below : On this basis of these placards the chemistry teacher, Mrs. Shanti, asked a student Vikas to answer the following questions : (a) Choose the symbol of an element from among the placards which exhibits valencies of 3 and 5. What is the name of is the name of this element ? Is it a metal or a non-metal ? (b) Choose the symbol of an element from the given placards which shows a valency of 2. What is the name of this element ? Is it a metal or a non-metal ? (c) Work out the formula of the compound formed between the element of valency 3 and element of valency 2. Also name this compound (d) What values are displayed by Vikas in this episode ?

Chemical formula of a molecular compound represents the actual number of atoms of different elements present in one molecule of the compound. With the help of symbols and valencies or charges, a formula can be made. First write the symbol such as positive ion to the left and negative ion to the right and then criss cross the valencies or charges . Thus in this way we can write a chemical formula. The valency of A is 2 and B is 1, a chemical formula formed by both of them will be

Chemical formula of a molecular compound represents the actual number of atoms of different elements present in one molecule of the compound. With the help of symbols and valencies or charges, a formula can be made. First write the symbol such as positive ion to the left and negative ion to the right and then criss cross the valencies or charges . Thus in this way we can write a chemical formula. The symbols needed to form barium chloride are

Case 1: A chemical equation is the representation of chemical change in terms of symbols and formulae of reactants and products. The substances which react are written on the left hand side of the arrow and are termed as reactants while the substances produced as result of reaction are called products and are written on the right hand side of the arrow. The arrowhead shows the direction of the reaction. A chemical equation in the whcih the number of atoms of each element on reactant side is equal to that on the product side is said to be balanced. Which of the following statement is incorrect regarding th significance of the chemical equations?

Case 1: A chemical equation is the representation of chemical change in terms of symbols and formulae of reactants and products. The substances which react are written on the left hand side of the arrow and are termed as reactants while the substances produced as result of reaction are called products and are written on the right hand side of the arrow. The arrowhead shows the direction of the reaction. A chemical equation in the which the number of atoms of each element on reactant side is equal to that on the product side is said to be balanced. In which of the following equation the mass is not same on both the sides?

Case 1: A chemical equation is the representation of chemical change in terms of symbols and formulae of reactants and products. The substances which react are written on the left hand side of the arrow and are termed as reactants while the substances produced as result of reaction are called products and are written on the right hand side of the arrow. The arrowhead shows the direction of the reaction. A chemical equation in the whcih the number of atoms of each element on reactant side is equal to that on the product side is said to be balanced. Among the following the correct balanced equation is

Case 1: A chemical equation is the representation of chemical change in terms of symbols and formulae of reactants and products. The substances which react are written on the left hand side of the arrow and are termed as reactants while the substances produced as result of reaction are called products and are written on the right hand side of the arrow. The arrowhead shows the direction of the reaction. A chemical equation in the whcih the number of atoms of each element on reactant side is equal to that on the product side is said to be balanced. How is input of energy represented in chemical equation ?