Assertion: Element X has electronic configuration 2, 8, 18, 8, 1. X will be a reducing agent.
Reason: X has a tendency to lose one electron.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
C. Assertion is correct but Reason is incorrect.
D. Both Assertion and Reason are incorrect.

Hint: If an element has a tendency to lose electrons then it is going to act as a good reducing agent and if an element has a tendency to accept electrons then it is going to act as a good oxidizing agent. The tendency to accept or lose electrons by an element is going to depend on the electronic configuration of the element.

Complete Solution :
- In the question it is given that an element X has 2, 8, 18, 8, 1 electrons in its electronic configuration.
- If any element has completely filled electrons in its valence shell then the element is more stable.
- In the same manner the element X to get stable electronic configuration or octet configuration it will lose the single electron and get octet configuration to get stability.
- Means the element X is going to lose its valence electron means it is going to act as a reducing agent.
- Therefore element X will lose electrons and acts as a reducing agent.
- So, Both Assertion and reason are correct and reason is the correct explanation for Assertion.
So, the correct answer is “Option A”.

Note: Here the element which has electronic configuration of 2, 8, 18, 8, 1 is Rubidium. The atomic number of Rubidium is 37 (nothing but the number of electrons present). The charge on the rubidium after losing one electron is ‘+1’.