21. Which of the following element has four valence electrons?
a. Silicon
b. Germanium
C. both A and B
d. None of the above

22. The total energy of an electron in an atom will be maximum when it is
a. closet to nucleus
b. in the even numbered orbit
c. odd numbered orbit
d. in an orbit farthest from the nucleus

23. Which of the following elements has four valence electron
a. silicon
b. antimony
c. phosphorous
d. boron

24. A germanium atom has
a. five valence electron
b. four protons
c. three valence electrons
d. two electrons orbit

25. If an electron move through a potential difference of 500 V , the energy possessed by it will be
a. 500 ergs
b. 500 joules
c. 500 eV
d. 500 mV

26. The forbidden energy gap for silicon is
a. 0.12 eV
b. 0.32 eV
c. 0.72 eV
d. 7.2 eV

27. The forbidden energy gap for germanium is
a. 0.12 eV
b. 0.32 eV
c. 0.72 eV
d. 0.92 eV

28. Free electrons exists in
a. first band
b. second band
c. third band
d. conduction band

29. The forbidden energy gap between the valence band and conduction band will be least in case of
a. metals
b. semi-conductors
c. insulators
d. all of the above

30. The forbidden energy gap between the valence band and conduction band will be wide in case of
a. semi-conductors
b. all metals
c. good conductor of electricity
d. insulators

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