Question

1. the molecule that has a molecular shape of trigonal pyramidal is _ i because _ ii

the statement above is best completed by the answers in row:
row i ii
□ ph₃ the central atom has a lone pair
□ bh₃ the central atom has a lone pair
□ ph₃ the central atom has no lone pairs
□ bh₃ the central atom has no lone pairs

Explanation:

Step1: Recall molecular - geometry rules

The molecular geometry of a molecule depends on the number of bonding pairs and lone - pairs around the central atom. For a trigonal - pyramidal shape, the central atom has 3 bonding pairs and 1 lone pair.

Step2: Analyze \(PH_3\) and \(BH_3\)

• In \(PH_3\), the central phosphorus (\(P\)) atom has 5 valence electrons. It forms 3 single bonds with hydrogen (\(H\)) atoms, using 3 of its valence electrons. So, there is 1 lone pair of electrons on the \(P\) atom (\(5 - 3=2\) non - bonding electrons or 1 lone pair). The electron - pair geometry around \(P\) is tetrahedral (\(3\) bonding pairs and \(1\) lone pair), and the molecular geometry is trigonal pyramidal.
• In \(BH_3\), the central boron (\(B\)) atom has 3 valence electrons. It forms 3 single bonds with hydrogen (\(H\)) atoms, using all of its valence electrons. There are no lone pairs on the \(B\) atom. The electron - pair geometry and molecular geometry of \(BH_3\) are trigonal planar.

Answer:

PH₃; the central atom has a lone pair