STRUCTURE OF ATOM 9

Practice Paper

Subject Chemistry (2020)

CH-4  Structure of Atom

Class IX 

                                                                      

I. Very short answer type questions:

1. Define atoms.
2. Write the name of particles present in atoms. or Write the name of subatomic particles.
3. Define atomic number.
4. Define mass numbers.
5. Define electronic configuration.
6. Write the formula for calculating the maximum no.of electrons in an orbit?
7. What happens to an element Z if its atom gain three electrons?
8. J Chadwick discovered a subatomic particle that has no charge and has a mass nearly equal to that of the proton. Name the particle and give its location in the atom?
9. Which one of the Na+ and He has completely filled K and L shells? Give a reason to support your answer. 
10. The atomic numbers of atoms of two elements are 18 and 20 respectively and their mass number is 40. What is the relation between such pairs of atoms? Will they have the same property?
11. Which elements have zero combining capacity or valency?
12. How many electrons can be accommodated in the outermost shell of an atom?
13. If the electronic configuration of an atom is 2, 8, 1, calculate the total number of electrons and write the name of the element.
14. What is the valency of oxygen if the atomic number is 8?
15. Who concluded that the size of the nucleus is very small compared to the size of an atom?

II. Short answer type questions:

1. Write the properties of electron, proton, and neutron.
2. An atom of an element has three electrons in its 3rd orbit which is the outermost shell and Write
   (i) the electronic configuration
   (ii) atomic number
   (iii) number of protons, electrons, neutrons
   (iv) valency.  
3. There are 16 protons and 15 Neutrons are present in an element. Calculate its atomic number and its atomic mass. State its valency.
4. If an element X is available in the form of say, two isotopes ⁷⁹Br₃₅ (49.7 %) and  ⁸¹Br₃₅ (50.5 %), calculate the average atomic mass of the atom of X.
5. An atom of an element is represented as ¹⁹Y₉ .
   Write the
   (a) The electronic configuration
   (b) Atomic number
   (c) No. of protons and
   (d) Valency.
6. The electronic configuration of an element X  is 2 , 8 , 2 :
   (a) Find the number of electrons present in the atom of element X.
   (b) Write its atomic number and
   (c) Its atomic mass.
7. List Bhor-bury rules for the distribution of electrons in different shells. Draw the atomic structure of an atom with atomic number 11.
8. Draw the atomic structure of an atom with atomic number 11.
9. Composition of the nuclei of two atomic species X and Y are given below.
   Element    X   Y
   Proton      8    8
   Neutron    8    10
   i. Give the mass number.
   ii. What is the relationship between the two elements?
10. Give one word of the following;
    (i) Positively charged atom.
    (ii) A group of atoms carrying a charge?
11.  (a) J. Chadwick discovered a subatomic particle that has no charge and has a mass nearly equal to that of the proton. Name the particle and give its location in the atom. 
    (b) k and L shells of an atom are completely filled electrons, then what would be (i). the total number of electrons in the atom and (ii). it's valency?
12. State three features of the nuclear model of an atom put forward by Rutherford. 
13. Mention the postulates Niels Bohr put forward to overcome the objection raised against Rutherford's atomic model. 
14. An element X has mass number 27 and it contains 13 protons.
    (a) Write the symbolic representation of the element.
    (b) Find the number of Neutrons in the element.
    (c) Write the name of the element.
15. Sulfur dioxide is a colorless pungent-smelling gas and is a major air pollutant.
    (a) Write the electronic configuration of its constituent element Sulphur and Oxygen. (Given - ³²S₁₆, ¹⁶O₈ )
    (b) Write the valency of Sulphur and Oxygen.
    (c) Are sulfur and Oxygen isotope? Explain your answer.
16. Calculate the average atomic mass of chlorine if it exists commonly in two isotopes. ³⁵Cl₁₇ (75%)   and   ³⁷Cl₁₇ (25%).
17. (a) What are the canal rays?  (b) State three characteristics of canal rays.
18. If ¹⁴X₆  is an isotope of element Y and has 2 neutrons less than X.
    (a) Write the symbol of element Y showing its mass number and atomic number.
    (b)Write the valency for these elements. What relation is given for the chemical properties of  X and Y.
19. An element ¹⁴X₁₂ loses two electrons to form a cation which combines with the anion of element  ³⁵X₁₇ formed by gaining an electron.
    (a) Write the electronic configuration of element X
    (b) Write the electronic configuration of the anion of Y
    (c) Write the formula of the compound formed by the combination of X and Y.
20. .(i) ²⁴Mg₁₂ and ²⁶Mg₁₂  are symbols of two isotopes of Mg. Compare atom of these isotopes with respect to
    (a) Composition of their nuclei.
    (b) Electronic configuration and valency.
    (ii) Give the reason why two isotopes of magnesium have different mass numbers?
21. Two elements X and Y combine in a ratio of 3 : 8  by mass and the compound Z is formed. Z is one of the essential components of photosynthesis to take place. If Z is also one of the greenhouse gases:
    (a) Identify the X,Y and Z.
    (b) Write the electronic configuration of X and Y.
    (c) Write the atomicity of the molecule of Z. 
22. If the mass no. of an element is 23 and its atomic no.is 11 then
    (a) Write its electronic configuration and its valency.
    (b) Find the no. of neutrons in its nucleus.
    (c) Mention the types of the ion formed by it.
23. State the difference between isotopes and isobar. Give an example of each.
24. Name the scientists who discovered Proton,  Electron, and Neutron.
25. What is the charge and mass of a neutron?

III. Long answer type questions:

1. Give reasons for the following:
   (a) An atom is electrically neutral.
   (b) Noble gases show the least reactivity.
   (c) The nucleus of an atom is heavy and positively charged.
   (d) Ions are more stable than an atom.
2. (a)A helium atom has an atomic mass of 4u and two protons in its nucleus. How many neutrons does it have?
   (b)The atomic mass of an element X is 16.2 u. What is the % age of isotope X having atomic number 8 and mass numbers 16 and 18?
3. How many electrons, protons and neutrons are there in an element  ¹⁹ X ₉ ? What will be the valency?
4. (a) Define isotope and isobar with examples.
   (b) What do the species ⁴B₂ and ⁴C₃ represent?
5. (a) List three subatomic particles of an element with its charge.
   
   (b) A helium atom has an atomic mass 4 u and it's atomic no. is 2. How many neutrons does it have?
6. Study the following table and answer the questions:
   

   Elements	Protons	Neutrons	Electrons
   A	2	3	2
   B	10	9	10
   C	17	20	16
   D	17	17	17
   E	18	19	18
   F	17	20	17

   (a) What is the mass no. of elements A and B?

   (b) What is the atomic no. of element B?
   (c) Which two elements represent a pair of isotope and why?
   (d) What is the valency of B and D?
   (e) Identify the cation.
   (f)  Identify a pair of isobar.
7. List three differences between electrons, protons, and neutrons.
8. What observation in alpha-particle scattering experiment is the Rutherford to make the following:

   
   

   a) Most of the space in an atom is empty. 

   
   

   b) The positive charge of the atom occupies very little space.

   
   

   c) The mass of the atom is concentrated in a very small volume within the atom.
9. (a) Which isotope is used in the treatment of cancer?
   (b) the particle contains 11 protons and 10 electrons. Write the symbol and name of the particles.
   (c) What do you think would be the observation if the alpha-particle scattering experiment is carried out using a foil of a metal other than gold.
10. (a) State the limitations of J.J. Thomson’s model of an atom.
    (b) Define valency by taking the example of Mg and O₂
    (c) S^-2 has completely filled K, L and M shells. Find its atomic number.

NCERT QUESTIONS:

1. What are the canal rays?
2. If an atom contains one electron and one proton, will it carry any charge or not?
3. On the basis of Thomson’s model of an atom, explain how the atom is neutral as a whole.
4. On the basis of Rutherford’s model of an atom, which a subatomic particle is present in the nucleus of an atom?
5. Draw a sketch of Bohr’s model of an atom with three shells.
6. What do you think would be the observation if the α-particle scattering experiment is carried out using a foil of a metal other than gold?
7. Name the three sub-atomic particles of an atom.
8. A helium atom has an atomic mass of 4 u and two protons in its nucleus. How many neutrons does it have?
9. Write the distribution of electrons in carbon and sodium atoms.
10. If K and L shells of an atom are full, then what would be the total number of electrons in the atom?
11. How will you find the valency of chlorine, sulphur, and magnesium?
12. If the number of electrons in an atom is 8 and the number of protons is also 8, then (i) what is the atomic number of the atom? and (ii) what is the charge on the atom?
13. For the symbol H, D and T tabulate three sub-atomic particles found in each of them.
14. Write the electronic configuration of any one pair of isotopes and isobars.
15. Compare the properties of electrons, protons, and neutrons.
16. What are the limitations of J.J. Thomson’s model of the atom?
17. What are the limitations of Rutherford’s model of the atom?
18. Describe Bohr’s model of the atom.
19. Compare all the proposed models of an atom given in this chapter.
20. Summarise the rules for the writing of distribution of electrons in various shells for the first eighteen elements.
21. Define valency by taking examples of silicon and oxygen.
22. Explain with examples (i) Atomic number, (ii) Mass number, (iii) Isotopes and iv) Isobars. Give any two uses of isotopes.
23. Na+ has completely filled K and L shells. Explain.
24. If bromine atom is available in the form of, say, two isotopes 79 35 Br (49.7%) and 81 35 Br (50.3%), calculate the average atomic mass of bromine atom.
25. The average atomic mass of a sample of an element X is 16.2 u. What are the percentages of isotopes 16 8 X and 18 8 X in the sample?
26. If Z = 3, what would be the valency of the element? Also, name the element.
27. Composition of the nuclei of two atomic species X and Y are given as under X Y Protons = 6 6 Neutrons = 6 8 Give the mass numbers of X and Y. What is the relation between the two species?
28. For the following statements, write T for True and F for False.
    (a) J.J. Thomson proposed that the nucleus of an atom contains only nucleons.
    (b) A neutron is formed by an electron and a proton combining together. Therefore, it is neutral.
    (c) The mass of an electron is about 1 2000 times that of the proton.
    (d) An isotope of iodine is used for making tincture iodine, which is used as a medicine.
29. Put a tick (✓) against correct choice and cross (×) against the wrong choice in questions i. ii, iii, and iv.
    (i)Rutherford’s alpha-particle scattering experiment was responsible for the discovery of
    (a) Atomic Nucleus (b) Electron (c) Proton (d) Neutron.
    (ii) Isotopes of an element have
    (a) the same physical properties    (b) different chemical properties
    (c) a different number of neutrons (d) different atomic numbers.
    (iii) Number of valence electrons in Cl– ion are: (a) 16 (b) 8 (c) 17 (d) 18.
    (iv) Which one of the following is a correct electronic configuration of sodium? (a) 2,8 (b) 8,2,1 (c) 2,1,8 (d) 2,8,1.

CHAPTER 1 - MATTER IN OUR SURROUNDINGS	☛ QUESTION WITH SOLUTIONS
CHAPTER 2 - IS MATTER AROUND US PURE?	☛QUESTION WITH SOLUTIONS
CHAPTER 3 - ATOMS AND MOLECULES	☛ QUESTION WITH SOLUTIONS
CHAPTER 4 - STRUCTURE OF ATOM	☛   QUESTION WITH SOLUTIONS
CHAPTER 5 -  THE FUNDAMENTAL UNIT OF LIFE
CHAPTER 6 -  TISSUE
CHAPTER 7 -   DIVERSITY IN LIVING ORGANISM
CHAPTER 8 -  MOTION	☛ QUESTION WITH SOLUTIONS
CHAPTER 9 -  FORCE AND LAW OF MOTION	☛  QUESTION WITH SOLUTIONS
CHAPTER 10 - GRAVITATION	☛ QUESTION WITH SOLUTIONS
CHAPTER 11 -  WORK AND ENERGY
CHAPTER 12 -  SOUND
CHAPTER 13-  WHY DO WE FALL ILL
CHAPTER 14 - NATURAL RESOURCES
CHAPTER 15 - IMPROVEMENT OF FOOD RESOURCES