The electronic configuration of an element is 1s², 2s² 2p6, 3s² 3p³. What is the atomic number of the element which is just below the above element in the periodic table

The correct option is 33.

Let us break down the explanation step-by-step to understand why this is correct.

Step 1: Determine the atomic number of the given element
The electronic configuration of the given element is:
$$1s^{2}2s^{2}2p^{6}3s^{2}3p^3$$
The total number of electrons in an atom of this element is equal to the sum of the electrons in each subshell:
Total electrons = 2 + 2 + 6 + 2 + 3 = 15.
For a neutral atom, the atomic number (Z) is equal to the number of electrons. Therefore, the atomic number of the given element is 15 (which is Phosphorus, P).

Step 2: Identify the position of the element in the periodic table
Looking at the electronic configuration, the highest principal quantum number (valence shell) is n = 3, meaning it belongs to the 3rd period.
The valence shell electronic configuration is $3s^{2}3p^3$, which has 5 valence electrons. This indicates that the element belongs to Group 15 (nitrogen family) of the periodic table.

Step 3: Find the atomic number of the element just below it
Elements in the same group of the periodic table follow a periodic pattern in atomic numbers. To move from an element in the 3rd period of Group 15 to the element directly below it in the 4th period, we add the capacity of the 4th period shell, which corresponds to adding 18 elements (since the 4th period contains 18 elements: transition metals are filled in between).
So, we compute:
Atomic number of the element below = Atomic number of the given element + 18
$$\text{Atomic number}=15+18=33$$
Thus, the element directly below it is Arsenic (As) with an atomic number of 33.