Answer
X=Se
Work Step by Step
To solve this problem, we need to determine the identity of the unknown element X based on the given information.
Given information:
- The polyatomic ion is composed of C, N, and an unknown element X.
- The skeletal Lewis structure of the polyatomic ion is [X-C-N]^-.
- The ion X^2- has an electron configuration of [Ar]4s^2 3d^10 4p^6.
Step 1: Identify the unknown element X.
The electron configuration of the ion X^2- indicates that the element X is selenium (Se).
The electron configuration of Se^2- is [Ar]4s^2 3d^10 4p^6, which matches the given information.
Step 2: Complete the Lewis structure of the polyatomic ion [X-C-N]^-.
The complete Lewis structure of the polyatomic ion [Se-C-N]^- is:
[Se=C=N]^-
This structure includes the following important resonance structures:
[Se=C=N]^-
[Se-C≡N]^-
The key points about the Lewis structure are:
- The central atom is selenium (Se), which forms a double bond with the carbon atom.
- The carbon atom forms a triple bond with the nitrogen atom.
- The overall charge of the polyatomic ion is -1.
