set 3 MCQ Questions & Answers Detailed Explanation

Question : 1

In an atom valence electron are present in

a) next to outermost orbit

b) first orbit

c) outermost orbit

d) any one of its orbit

Question : 2

The alpha particle carries two positive charges. Its mass is very nearly equal to that of

a) An atom of helium

b) Sum of masses of two positrons and two neutrons

c) Two protons

d) Two positrons are each positron carries a single positive charge

Question : 3

While performing cathode ray experiments, it was observed that there was no passage of electric current under normal conditions. Which of the following can account for this observation ?

a) Carbon dioxide is present in air

b) Air is a poor conductor of electricity under normal conditions

c) Dust particles are present in air

d) None of these

Question : 4

Which one among the following is correct regarding ²⁰Ne, ²³Na+, ¹⁹F– and ²⁴Mg²⁺?

a) They are isoelectronic with each other

b) They are isotopes of each other

c) They are isomers of each other

d) All of the above

Question : 5

The Nucleus of Helium has

a) Two protons

b) Two protons and two neutrons

c) Only one neutron

d) One proton and two neutrons