Questions: Use the interactive window below to build the Lewis structure of SeCl3+. Consider the positive charge when counting the number of electrons. You do not need to label the positive charge or include brackets. Turn on the Formal Charge Tracker to see which atom bears the positive formal charge in the complete Lewis structure.

Solution Steps

To build the Lewis structure of $\mathrm{SeCl}_{3}^{+}$, we first need to determine the total number of valence electrons. Selenium (Se) has 6 valence electrons, and each chlorine (Cl) has 7 valence electrons. Since there are three chlorine atoms, we have:

$$6 + 3 \times 7 = 27 \text{ valence electrons}$$

However, because the molecule has a positive charge, we subtract one electron:

$$27 - 1 = 26 \text{ valence electrons}$$

Next, we draw the skeletal structure with selenium (Se) as the central atom and three chlorine (Cl) atoms bonded to it. Each bond represents 2 electrons.

After placing the bonds, we distribute the remaining electrons to satisfy the octet rule for each atom. Each Se-Cl bond uses 2 electrons, so:

$$3 \times 2 = 6 \text{ electrons used in bonds}$$

Subtracting these from the total valence electrons:

$$26 - 6 = 20 \text{ electrons remaining}$$

Each chlorine atom needs 8 electrons to complete its octet. Since each Cl already has 2 electrons from the bond, each needs 6 more electrons:

$$3 \times 6 = 18 \text{ electrons for Cl atoms}$$

Subtracting these from the remaining electrons:

$$20 - 18 = 2 \text{ electrons remaining}$$

The remaining 2 electrons are placed on the selenium atom.

Finally, we check the formal charges to ensure the structure is correct. The formal charge is calculated as:

$$\text{Formal charge} = \text{Valence electrons} - \text{Non-bonding electrons} - \frac{\text{Bonding electrons}}{2}$$

For selenium: $$6 - 2 - \frac{6}{2} = 6 - 2 - 3 = +1$$

For each chlorine: $$7 - 6 - \frac{2}{2} = 7 - 6 - 1 = 0$$

The positive charge is on the selenium atom, which matches the given $\mathrm{SeCl}_{3}^{+}$.

Final Answer