7. How does valency vary in a group and in a period of the Periodic Table?
8.
Why do elements of the same group have similar properties?
9. What is meant by a molecular formula? Write the molecular formulae of carbon dioxide, copper
sulphate, nitric acid and hydrogen sulphide.
Answers
Answer:
7)The valency of an element is dependent on the number of electrons in the outermost shell of the electron. In a group all constituting elements will have the same valency because they all have the same number of electrons in the outer shells. Across the a period, the number however increase by 1.
8) (a) (i) All the elements of a group have similar chemical properties because they have same no. of valence electrons in their outermost shell.
(ii) All the elements of a period have different chemical properties because they have different no.
9) A chemical formula that gives the total number of atoms of each element in each molecule of a substance.
Carbon dioxide=CO2
Copper sulphate=CuSO4
Nitric acid=HNO₃
Hydrogen sulphide=H₂S
Explanation:
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