39. Atoms of an element differ from those of all other elements in : [Hotel Management 1993]
    (a) atomic number and electronic configuration
    (b) atomic number and number of valency electrons
    (c) number of neutrons and electronic configuration
    (d) number of neutrons and number of valence electrons
Ans: (a)
40. Match the following: [NDA 1990]
    Particle       Charge
    A. α particle  1. + 2e
    B. β particle  2. - e
    C. Neutron     3. Zero
    D. Proton      4. + e
         A         B         C        D
    (a)  1         2         3        4
    (b)  2         4         3        1
    (c)  3         2         1        4
    (d)  4         3         2        1
Ans: (a)
41. Match the following:
    A. Isotopes    1. Atoms having same atomic number but different mass numbers
    B. Isobars     2. Atoms with same number of neutrons but different atomic numbers
    C. Isotones    3. Atoms with same mass number but different atomic numbers
         A         B         C
    (a)  1         2         3
    (b)  1         3         2
    (c)  2         3         1
    (d)  2         1         3
Ans: (b)
42. An atom of an element with mass number 23 and atomic number 11 will have:
    (a) 11 neutrons, 12 protons and 11 electrons
    (b) 11 protons, 12 neutrons and 11 electrons
    (c) 11 neutrons, 11 protons and 12 electrons
    (d) 23 protons arid 11 electrons
Ans: (b)
43. Match the following: - [NDA 1990]
    Compound added           Colour imparted to glass
    A. Manganese dioxide 1. Yellow
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