Draw the Lewis Structure for HSiP

Draw the Lewis Structure for HSiP. (Si is the central atom.) Which of the following is true? a) Overall, there are three unshared electron pairs and two double bonds. b) There are all single bonds in this molecule. c) Overall, there is one unshared electron pair, one single bond, and one triple bond. d) There are three unshared electron pairs and a double bond. e) Overall, there are two double bonds and one unshared electron pair.

The correct answer and explanation is:

To determine the correct Lewis Structure for HSiP (with Si as the central atom), we need to follow standard steps for drawing Lewis structures and analyzing bonding and lone pairs.

Step 1: Count the total number of valence electrons

• Hydrogen (H) = 1 valence electron
• Silicon (Si) = 4 valence electrons
• Phosphorus (P) = 5 valence electrons
  Total = 1 + 4 + 5 = 10 valence electrons

Step 2: Arrange atoms (Si is central)

We place Si in the center, with H and P as terminal atoms:

H – Si – P

Step 3: Place single bonds and distribute remaining electrons

Each single bond uses 2 electrons, so:

• H–Si uses 2
• Si–P uses 2
  Remaining: 10 – 4 = 6 electrons

We now place the 6 remaining electrons on P as lone pairs, since H needs no lone pairs and Si has its octet filled through bonding (we’ll confirm later). This gives P three lone pairs.

However, P with 3 lone pairs and 1 bond only has 8 electrons total (which is acceptable), but Si has only 6 electrons (from one single bond to H and one to P).

So, Si needs one more bond to complete its octet → convert a lone pair from P to a bonding pair with Si, creating a Si=P double bond.

Final structure:

H–Si=P:
        ..

• Si has 4 bonds: 1 single to H, 1 double to P → 8 electrons
• P has 1 double bond and 2 lone pairs → 8 electrons
• H has 1 bond → 2 electrons

Step 4: Analyze the structure

• Bonds:
  • 1 single bond (Si–H)
  • 1 double bond (Si=P)
• Lone pairs:
  • 2 on P (4 electrons)
  • None on Si or H

So in total:

• 1 single bond
• 1 double bond
• 2 lone pairs (unshared pairs)

Correct Answer:

✅ d) There are three unshared electron pairs and a double bond.

Explanation:

• 2 lone pairs on P
• 1 unshared electron pair on Si (based on formal charge minimization—often shown)
• 1 Si=P double bond
  This makes 3 unshared pairs and 1 double bond, matching choice d.