Question

When Carbon $- 14$ undergoes beta (electron) decay, it transmutes into what?
A. Carbon $- 13$
B. Carbon $- 12$
C. Nitrogen $- 13$
D. Nitrogen $- 12$
E. Nitrogen $- 14$

Answer 1

In radioactivity, when an atom of nucleus undergoes decay it means either it accept some nuclei such as helium or an electron or in some cases it emits these types of nuclei, such decaying processes are known as radioactive decay.

Complete step by step answer:
As we know that the atomic number of a carbon atom is $6$ and when we say Carbon $- 14$ we mean the atomic mass of this nuclei is $14$ and it can be written as $^{14}{C_6}$.In beta (electron) decay, the nuclei which undergoes this beta radioactive decay it loses one of its electron and thus forming new nuclei with having one more number of electron. One more electron means the atomic number of nuclei will increase by one.

So, we can write this radioactive decay process as follows:
Beta (electron) decay of Carbon $- 14$ is:
$^{14}{C_6}{ \to ^A}{X_Z}{ + ^0}{e_{ - 1}}$
Here, let us assume that the newly formed nucleus is $X$ whose atomic mass will be the same as that of carbon which is $14$ and its atomic number denoted by $Z$ will get increased by one and it will become $7$. So , the equation can be now written as
$^{14}{C_6}{ \to ^{14}}{X_7}{ + ^0}{e_{ - 1}}$
So the formed nucleus is $^{14}{N_7}$ Nitrogen.

Hence, the correct option is E.

Note: In radioactivity, some of the unstable nuclei undergo various types of decay to become stable nuclei and this some amount of radiation may release or sometimes nuclei gain some radiation as a form of energy for completing the decay process. Nitrogen has an atomic number of $7$ and has atomic mass of $14$ .