What is the hybridization of the central atom in NH3? A sp3 B sp2 C sp D sp3d QUESTION 4 Which of the following pairs of molecules have the same geometry? A H2O and CS2 B BeCl2 and CO2 C BF3 and NH3 D CH4 and NH3
The Correct Answer and Explanation is:
Hybridization of the Central Atom in NH3:
In ammonia (NH3), the central nitrogen (N) atom has three single bonds with three hydrogen atoms, and it also has one lone pair of electrons. To determine the hybridization of the nitrogen atom, we need to look at the electron pairs around the nitrogen atom:
- Number of electron pairs around nitrogen: 3 (from bonding with H) + 1 (lone pair) = 4 electron pairs.
Since nitrogen has 4 electron pairs, the electron geometry of the molecule is tetrahedral. For a molecule with 4 electron pairs, the hybridization of the central atom is sp3.
Therefore, the correct answer is: A. sp3
Geometry of the Molecules:
Let’s now examine the second question about which pairs of molecules have the same geometry. We’ll analyze the geometry of each molecule based on their bonding and electron pair arrangements:
- H2O (Water): Oxygen has two bonding pairs (with hydrogen) and two lone pairs of electrons. This gives a bent or V-shaped geometry with a bond angle of approximately 104.5°. CS2 (Carbon Disulfide): Carbon in CS2 forms two double bonds with sulfur, and since there are no lone pairs on the central atom, the molecule has a linear geometry with a bond angle of 180°. Conclusion: H2O and CS2 do not have the same geometry.
- BeCl2 (Beryllium Chloride): Beryllium in BeCl2 forms two single bonds with chlorine and has no lone pairs. This gives a linear geometry with a bond angle of 180°. CO2 (Carbon Dioxide): Carbon in CO2 forms two double bonds with oxygen, and like BeCl2, it has a linear geometry with a bond angle of 180°. Conclusion: BeCl2 and CO2 have the same geometry (linear).
- BF3 (Boron Trifluoride): Boron in BF3 forms three single bonds with fluorine and has no lone pairs. This gives a trigonal planar geometry with a bond angle of 120°. NH3 (Ammonia): Nitrogen in NH3 forms three single bonds with hydrogen and has one lone pair, resulting in a trigonal pyramidal geometry with a bond angle of approximately 107°. Conclusion: BF3 and NH3 do not have the same geometry.
- CH4 (Methane): Carbon in CH4 forms four single bonds with hydrogen and has no lone pairs. This results in a tetrahedral geometry with a bond angle of 109.5°. NH3 (Ammonia): As discussed above, NH3 has a trigonal pyramidal geometry, so it does not have the same geometry as CH4. Conclusion: CH4 and NH3 do not have the same geometry.
Correct Answer:
B. BeCl2 and CO2 both have the same linear geometry.
