Question

Consider the following statements :
A. Atoms of each element emit characteristics spectrum.
B. According to Bohr's Postulate, an electron in a hydrogen atom, revolves in a certain stationary orbit.
C. The density of nuclear matter depends on the size of the nucleus.
D. A free neutron is stable but a free proton decay is possible.
E. Radioactivity is an indication of the instability of nuclei. Choose the correct answer from the options given below:

• A. $A, B, C, D$ and $E$
• B. $A, B$ and $E$ only
• C. $B$ and $D$ only
• D. $A, C$ and $E$ only

Answer 1

Answer: (B)

(A) True, atom of each element emits characteristic spectrum.
(B) True, according to Bohr's postulates $m v r=\frac{n h}{2 \pi}$ and hence electron resides into orbits of specific radius called stationary orbits.
(C) False, density of nucleus is constant
(D) False, $A$ free neutron is unstable decays into proton and electron and antineutrino.
(E) True unstable nucleus show radioactivity.