Question

write condensed electron configuration and partial diagram for Se^2- and explain why?

Answer 1

To write the condensed electron configuration for the selenide ion (Se²⁻), we start by considering the atomic configuration of neutral selenium (Se).

**1. Neutral Selenium (Se) Configuration:**
Selenium has an atomic number of 34. The electron configuration for neutral Se is:

\[
\text{[Ar]} 4s^2 3d^{10} 4p^4
\]

**2. Adding Electrons for Se²⁻:**
The selenide ion (Se²⁻) has gained 2 additional electrons. These electrons will be added to the next available orbitals, which are the 4p orbitals.

**3. Electron Configuration for Se²⁻:**
After adding two electrons to selenium, the electron configuration for Se²⁻ becomes:

\[
\text{[Ar]} 4s^2 3d^{10} 4p^6
\]

This can be summarized as:

**Condensed Electron Configuration:**
\[
\text{Se}^{2-}: \text{[Ar]} 4s^2 3d^{10} 4p^6
\]

**4. Explanation:**
- **Why Se²⁻?** Selenium typically gains two electrons to achieve a stable electron configuration similar to that of the nearest noble gas, krypton (Kr), which has a completed outer electron shell (octet). The stable configuration minimizes energy, making the ion more stable than the neutral atom.
- The filled 4p subshell (4p⁶) reflects that the ion has achieved the electron configuration of a noble gas, which is a common reason for elements to form anions.

**Partial Diagram:**
To visually represent the electron configuration, you can depict the electrons filling the orbitals:

```
Orbital: 4s 3d 4p
Electrons: ↑↓ ↑↑↑↑↑↑ ↑↑↑↑↑↑
```

Here, "↑" represents unpaired electrons, and "↓" indicates paired electrons. The 4s subshell has 2 electrons, the 3d subshell has 10 electrons, and the 4p subshell has 6 electrons in the Se²⁻ ion.