In the Lewis dot structure of PH3, how many single bonds are there and how many non bonding pairs of electrons are in the central atom?
The Correct Answer and Explanation is :
In the Lewis dot structure of PH₃ (phosphine), there are three single bonds and one non-bonding pair of electrons on the central atom (phosphorus).
Explanation:
- Determining Valence Electrons: To draw the Lewis structure, first, we need to determine the total number of valence electrons for the molecule. Phosphorus (P) is in Group 15 of the periodic table and has five valence electrons. Hydrogen (H), being in Group 1, has one valence electron. Since there are three hydrogen atoms in PH₃, the total number of valence electrons can be calculated as follows:
- Valence electrons from phosphorus: 5
- Valence electrons from three hydrogens: (3 \times 1 = 3)
- Total valence electrons: (5 + 3 = 8)
- Bonding Electrons: In the Lewis structure, we form bonds between the central atom and surrounding atoms. Each single bond consists of two electrons. In PH₃, phosphorus forms three single bonds with three hydrogen atoms. Therefore, the three single bonds use (3 \times 2 = 6) electrons.
- Non-bonding Pairs: After using 6 electrons for bonding, we have (8 – 6 = 2) electrons remaining. These remaining electrons are placed as a non-bonding pair on the phosphorus atom.
- Final Structure: The resulting Lewis structure of PH₃ shows phosphorus in the center with three hydrogen atoms bonded to it. The three single bonds are represented by lines connecting phosphorus to each hydrogen, and the non-bonding pair of electrons is depicted as a pair of dots next to phosphorus. This arrangement satisfies the octet rule for the hydrogen atoms (each has two electrons) while phosphorus retains its capacity to hold more than eight electrons.
In summary, PH₃ features three single bonds and one non-bonding pair of electrons on the phosphorus atom, showcasing the bonding characteristics of phosphorus in a molecular context.