CBSE Important Questions(Short questions) for Atoms and Molecules

Given below are the Class 9 Science Important Questions for CBSE Important Questions(Short questions) for Atoms and Molecules
a) Concepts questions
b) Calculation problems
c) Multiple choice questions
d) Long answer questions
e) Fill in the blank's
1. What is meant by the term chemical formula?
2. State the postulates of Dalton’s atomic theory which indicates the law of constant proportions?
3. Name two scientists who established the laws of chemical combination?
4. Give two drawbacks of Dalton’s atomic theory?
5. What is meant by a molecule? Give examples?
6. What formed the basis for John Dalton to formulate Dalton’s atomic theory?
7. State the law of conservation of mass. Is this law applicable to the chemical reactions? Elaborate your answer with the help of an example?
8. Write down the formulae of:
a) Sodium oxide
b) Aluminium chloride
c) Sodium Sulphide
d) Magnesium hydroxide
9. State any four postulates of Dalton’s atomic theory of matter. Which of his postulates does not hold correct at present?
10. Write down the name of the following compounds:
a) KNO3
b) CaCO3
c) Ca(HCO3)2
11. When 3.0g of magnesium is burnt in 2.00g of oxygen, 5.00g of magnesium oxide is produced. What mass of magnesium oxide will be formed when 3.00g magnesium is burnt in 5.00g of oxygen? Which law of chemical combination will govern your answer?
12. write the symbol and Latin name of the following elements:
a) sodium
b) Potassium
13. Name the international organization which approves the names given to the elements?
14. ‘Atoms of most elements are not able to exist independently’. Name two atoms which exist as independent atoms?
15. What is the difference between an atom and a molecule?
16. Define atomic mass unit? State how do atoms exist?
17. The atomic number of three elements A, B, and C are 9, 10, and 13respectively. Which of them will form a cation?
18. How would you differentiate between a molecule of element and a molecule of compound? Write one example of each type?
19. Write atomicity of the following:
a) Sulphur
b) Phosphorus
20. State two examples in each case and write their chemical formulae:
a) Molecules having one kind of atoms only.
b) Molecules having two different kinds of atoms.
c) Molecules having three different  kinds of atoms.
21. Define atomicity?
22. State the atomicity of the following:
a. Oxygen
b. Phosphorus
c. Argon
23. Define polyatomic ion?
24. Write the name of the compound (NH4)2SO4 and mention the ions present in it?
25. Why do some atoms react with other atoms to form compounds where as some do not?

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