Question

Complete the following sentence:
The atomic number of a radioactive element is not changed when it emits _________.
A) $\gamma -radiations$
B) $\alpha -radiations$
C) $\beta -radiations$
D) None of the above

Answer 1

Radiation is energy given off by matter in the form of rays or high-speed particles. All matter is composed of atoms. The nucleus of an atom carries a positive electrical charge, while the electrons carry a negative electrical charge. The electrostatic and nuclear forces within the atom work toward a stable state by getting rid of excess atomic energy through a process called radioactivity, where an unstable nucleus may emit some energy, and this spontaneous emission is what we refer to as radiation.

Complete solution:
A gamma-ray, or gamma radiation, is a high-frequency form of electromagnetic radiation produced by the radioactive decay of atomic nuclei. It consists of electromagnetic waves having the shortest wavelength and hence the highest frequency and energy. The daughter nucleus that results is usually left in an excited state, without any change in the atomic number or the mass number of the element.
Gamma decay can be represented with the help of the following equation:
${}_{X}^{Y}A\to {}_{X}^{Y}A+\gamma$
Hence we can say that gamma particles are a form of energy and do not cause any change in the atomic number of a radioactive element.

Therefore, (A) is the correct option.

Note: Let us see what the other options mean and why they cannot be the correct answer.
Alpha particles consist of two protons and two neutrons bound together into a particle and can be referred to as a polarised helium atom. Hence alpha emission reduced the atomic number of an element by two and the mass number by four. A beta-particle is a high-energy electron emitted by the radioactive decay of an atomic nucleus. Beta emission increases the atomic number of an element by one.