Question

An element has $13$ electrons in its M shell and $1$ electron in N shell in ground state. Name the element.
a) Chromium
b) Iron
c) Manganese
d) Copper

Answer 1

The name of the element can be identified by counting the number all the electrons present in its all shells as it will give us the atomic number of that electron.

Complete step by step answer:
since we are provided with $13$electrons in M shell which means that these electrons belong to the third shell and also there is a single electron in N shell which means that it belongs to the fourth shell. From the above information, we can easily write down the electronic configuration which will help us in identifying that particular element. For 18 electrons belonging to the third shell we have $3{s^2}3{p^6}3{d^5}$ and for one electron belonging to the fourth shell we have $4{s^1}$. The electronic configuration of the element is $1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}3{d^5}4{s^1}$. Now we can identify the element by counting the number of electrons which is equal to $24$and that element is chromium.
So, the correct option is A.

Additional information: Principal quantum number(n) gives us the information about the name, size and energy of the shell to which the electron belongs.
The value of n lies between 1 to $\infty$.
Greater the value of n, greater is the distance from the nucleus.
Greater the value of n, greater is the energy.

Note:
The electronic configuration of an element is always written in increasing order of energy.
For neutral atom: The number of proton is equal to number of electron
For charged atoms: The number of protons is equal to the atomic number minus charge on an atom.