Science - Class 9

Q1. Elements with valency 1 are

(a) always metals

(b) always metalloids

(c) either metals or non-metals

(d) always non-metals.

 

Q2. The first model of an atom was given by

(a) N. Bohr

(b) E. Goldstein

(c) Rutherford

(d) J.J. Thomson

 

Q3. Rutherford’s alpha-particle scattering experiment was responsible for the discovery of

(a) Atomic Nucleus (b) Electron

(c) Proton              (d) Neutron

 

Q4. Isotopes of an element have

(a) the same physical properties

(b) different chemical properties

(c) different number of neutrons

(d) different atomic numbers.

 

Q5. Which of the following are true for an element?

(i)    Atomic number = number of protons + number of electrons

(ii)   Mass number = number of protons + number of neutrons

(iii) Atomic number = number of protons = number of neutrons

(iv) Atomic number = number of protons = number of electrons

(a) (i) and  (ii)     (b) (i) and  (iii)    (c) (ii) and (iii)    (d) (ii) and (iv)

 

Q6. Atomic models have been improved over the years. Arrange the following atomic models in the order of their chronological order

(i) Rutherford’s atomic model

(ii) Thomson’s atomic model

(iii) Bohr’s atomic model

(a) (i), (ii) and (iii)

(b) (ii), (iii) and (i)

(c) (ii), (i) and (iii)

(d) (iii), (ii) and (i)

 

Q7. Is it possible for the atom of an element to have one electron, one proton and no neutron? If so, name the element.

 

Q8. If bromine atom is available in the form of, say, two isotopes 
 , calculate the average atomic mass of bromine atom.

 

Q9. The electron distribution in an aluminium atom is

(a) 2,8,3

(b) 2,8,2

(c) 8,2,3

(d) 2,3,8

 

Q10. The atomic number of calcium and argon are 20 and 18 respectively, but the mass number of both these elements is 40. What is the name given to such a pair of elements?

 

Q11. Name the three sub-atomic particles of an atom.

 

Q12. In the atom of an element X, 6 electrons are present in the outermost shell. If it acquires noble gas configuration by accepting requisite number of electrons, then what would be the charge on the ion so formed?

 

Q13. Why did Rutherford select a gold foil in his α-ray scattering experiment?

 

Q14. If Z = 3, what would be the valency of the element? Also, name the element.

 

Q15. On the basis of Rutherford’s model of an atom, which subatomic particle is present in the nucleus of an atom?

 

Q16. One electron is present in the outermost shell of the atom of an element X. What would be the nature and value of charge on the ion formed if this electron is removed from the outermost shell?

 

Q17. 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.

 

Q18. Which of the following correctly represent the electronic distribution in the Mg atom?

(a) 3, 8, 1      (b) 2, 8, 2      (c) 1, 8, 3       (d) 8, 2, 2

 

Q19. An atom with 3 protons and 4 neutrons will have a valency of

(a) 3     (b) 7      (c) 1     (d) 4

 

Q20. Which of the following statement is always correct?

(a) An atom has equal number of electrons and protons.

(b) An atom has equal number of electrons and neutrons.

(c) An atom has equal number of protons and neutrons.

(d) An atom has equal number of electrons, protons and neutrons.

 

Q21. Calculate the number of neutrons present in the nucleus of an element  which is represented . 

 

Q22. Rutherford’s alpha (α) particles scattering experiment resulted into discovery of

(a) electron                         (b) proton

(c) nucleus in the atom         (d) atomic mass

 

Q23. If an atom contains one electron and one proton, will it carry any charge or not?

 

Q24. 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?

 

Q25. Dalton’s atomic theory successfully explained.

(i) Law of conservation of mass

(ii) Law of constant composition

(iii) Law of radioactivity

(iv) Law of multiple proportion

(a) (i), (ii) and (iii)

(b) (i), (iii) and (iv)

(c) (ii), (iii) and (iv)

(d) (i), (ii) and (iv).

 

Q26. Complete the table on the basis of information available in the symbols given below.