A      B    C     D
   (a) 4      1    2     3
   (b) 4      3    1     2
   (c) 4      2    1     3
   (d) 3      4    2     1
Ans: (c)
319. In the nucleus of an atom, the uncharged particle is
   (a) proton
   (b) neutron
   (c) electron
   (d) positron
Ans: (b)
320. Which of the following revolves round the nucleus in an atom?
   (a) protons
   (b) electrons
   (c) neutrons
   (d) positrons
Ans: (b)
321. The number of electrons in the outer orbits of a nucleus gives
   (a) the mass number
   (b) atomic number
   (c) atomic weight
   (d) absolute number
Ans: (b)
322. The radius of an atom is approximately
   (a) 10-10 cm
   (b) 10-12 cm
   (c) 10-13 cm
   (d) 10-16 cm
Ans: (a)
323. Besides protons, the nucleus of an atom contains
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