Selenium dioxydifluoride (SeO2F2), features a central selenium atom double-bonded to two oxygen atoms and single-bonded to two fluorine atoms, forming a distorted tetrahedral (pseudo-octahedral) geometry. Here is its lewis structure and steps to draw it.

Step 1: Calculate total valence electrons

Se: Group VIA, 6

O: 6 × 2 = 12

F: 7 × 2 = 14

Total valence electrons: 6 + 12 + 14 = 32 e?

Step 2: Determine the central atom

Se has the lowest electronegativity and, being in the fourth period, can accommodate an expanded octet; thus, it is the central atom.

Skeletal structure: Se forms double bonds with the two O atoms and single bonds with the two F atoms.

Step 3: Construct the σ-bond framework

Central atom Se, with four σ-bonds in the framework: 2 × Se–O and 2 × Se–F;

Add a π-bond to each of the two Se–O bonds to form two Se=O double bonds and two Se–F single bonds. Bonding electron count:

2 double bonds = 4 shared electron pairs; 2 single bonds = 2 shared electron pairs;

Total shared electron pairs = 6; total bonding electrons = 6 × 2 = 12 e?

Remaining electrons: 32 ? 12 = 20 e?

Step 4: Distribute lone pairs to peripheral atoms

Double-bonded O: Each O already has 4 bonding electrons; needs 2 lone pairs (4 e?) to satisfy the octet rule

Total lone electrons for 2 O atoms: 2 × 4 = 8 e?

Single-bonded F: Each F already has 2 bonding electrons; needs 3 lone pairs (6 e?) to satisfy the octet rule

Total lone electrons for 2 F atoms: 2 × 6 = 12 e?

Total peripheral lone pair electrons: 8 + 12 = 20 e?

Step 5: Electron verification

Bonding electrons (12) + peripheral lone pair electrons (20) = 32 e?; matches total valence electron count

No remaining lone electrons on central Se

Expanded octet check

Se bonding electrons: 2 double bonds (8 e?) + 2 single bonds (4 e?) = 12 e?; Period 4 elements can accommodate an expanded octet.