Question

The electronic configuration of an element is $1s^2,2s^2 2p^6,3s^2 3p^3$. What is the atomic number of the element, which is present just below the above element in the periodic table?

• A. 33
• B. 34
• C. 36
• D. 49

Answer 1

The Correct Option is A

 To determine the atomic number of the element below the given element in the periodic table, we must first identify the current element based on its electronic configuration and then locate the element beneath it in the same group (column).

Given electronic configuration: \(1s^2, 2s^2 2p^6, 3s^2 3p^3\).

1. The given configuration can be broken down as follows:
   • \(1s^2\): 2 electrons
   • \(2s^2 2p^6\): 8 electrons
   • \(3s^2 3p^3\): 5 electrons
2. Total number of electrons = \(2 + 8 + 5 = 15\).
3. The atomic number, \(Z\), is the same as the number of electrons in a neutral atom. So, \(Z = 15\).
4. Element with atomic number 15 is Phosphorus (P), which is in group 15 in the periodic table.

We need to find the element directly below Phosphorus in the periodic table, which is in group 15 and one period below.

The element immediately below Phosphorus (P) is Arsenic (As), with atomic number 33.

Therefore, the atomic number of the element below Phosphorus is \(33\).

Based on these observations, the correct answer is:

Option	Element
33	Arsenic (As)
34	Selenium (Se)
36	Krypton (Kr)
49	Indium (In)

Hence, the atomic number of the element below the given element is 33.