Consider the Lewis structure of CH3Cl. What is the best description of the molecular geometry? bent square square pyramidal tetrahedral 2. Which molecule has exactly two unshared (lone) pairs of electrons on the central atom? BF3 NF3 OF2 XeF2 3. What is the shape of the XeF4 molecule? square planar tetrahedral trigonal bipyramidal trigonal pyramidal 4. Which pair of molecules are geometrically similar? CO2 and OF2 PH3 and BF3 SO2 and CO2 SO2 and O3 5. What shape best describes the methyl cation, CH3+? linear octahedral tetrahedral trigonal planar 6. Which molecule has a non-linear structure? C2H2 CO2 H2O HCl 7. The Lewis structure of HCN (H bonded to C) shows that _ has _ nonbonding electron pairs. C, 1 H, 1 N, 1 N, 2 8. Based on the Lewis structure, the number of electron domains in the valence shell of the boron atom in the BF3 molecule is _. 1 2 3 4 9. Which one of the following arrangements would best accommodate five electron domains in the valence shell of a covalently bonded atom? planar triangular tetrahedral trigonal bipyramidal trihedral 10. All of the geometries listed below are examples of the five basic geometries for molecules with more than 3 atoms except octahedral tetrahedral trigonal bipyramidal trihedral
The Correct Answer and Explanation is:
Let’s break down each of the questions and their answers with explanations.
- What is the best description of the molecular geometry of CH₃Cl?
- Answer: Tetrahedral
- Explanation: In CH₃Cl, the central atom (carbon) is bonded to three hydrogens and one chlorine atom. Since there are four regions of electron density (three single bonds and one lone pair on carbon), the geometry is tetrahedral according to the VSEPR (Valence Shell Electron Pair Repulsion) theory.
- Which molecule has exactly two unshared (lone) pairs of electrons on the central atom?
- Answer: OF₂
- Explanation: In OF₂, the oxygen atom is the central atom and has two lone pairs of electrons. Oxygen is bonded to two fluorine atoms. According to VSEPR theory, this leads to a bent molecular geometry, and oxygen retains two lone pairs.
- What is the shape of the XeF₄ molecule?
- Answer: Square planar
- Explanation: In XeF₄, the central xenon atom is surrounded by four fluorine atoms and has two lone pairs. The electron pairs arrange themselves in a square planar geometry to minimize repulsion.
- Which pair of molecules are geometrically similar?
- Answer: CO₂ and SO₂
- Explanation: Both CO₂ and SO₂ have a linear molecular geometry. In CO₂, the carbon atom is double-bonded to two oxygen atoms, while in SO₂, the sulfur atom is double-bonded to two oxygen atoms as well, resulting in a similar linear shape for both molecules.
- What shape best describes the methyl cation, CH₃⁺?
- Answer: Trigonal planar
- Explanation: The CH₃⁺ ion has three bonding pairs of electrons around the central carbon atom (with no lone pairs), leading to a trigonal planar geometry. The positive charge means the carbon atom has no lone pairs, and the electron cloud is evenly distributed in a plane.
- Which molecule has a non-linear structure?
- Answer: H₂O
- Explanation: Water (H₂O) has a bent or non-linear structure because the oxygen atom has two lone pairs, which causes a repulsion between them, pushing the hydrogen atoms closer together. This results in a bond angle of about 104.5°, which is less than the ideal tetrahedral angle of 109.5°.
- The Lewis structure of HCN (H bonded to C) shows that __________ has __________ nonbonding electron pairs.
- Answer: N, 1
- Explanation: In HCN, nitrogen is the central atom, and it has one lone pair of electrons. The carbon is triple-bonded to nitrogen and bonded to hydrogen, leaving nitrogen with one lone pair.
- Based on the Lewis structure, the number of electron domains in the valence shell of the boron atom in the BF₃ molecule is _____.
- Answer: 3
- Explanation: In BF₃, boron is bonded to three fluorine atoms, each through a single bond. Since there are three bonding regions of electron density around boron, there are three electron domains.
- Which one of the following arrangements would best accommodate five electron domains in the valence shell of a covalently bonded atom?
- Answer: Trigonal bipyramidal
- Explanation: A trigonal bipyramidal arrangement accommodates five electron domains, with three electron pairs forming an equatorial plane and two forming axial positions, minimizing repulsion between the electron domains.
- All of the geometries listed below are examples of the five basic geometries for molecules with more than 3 atoms except?
- Answer: Trihedral
- Explanation: The five basic molecular geometries are linear, trigonal planar, tetrahedral, trigonal bipyramidal, and octahedral. Trihedral is not one of the basic molecular geometries used to describe molecular shapes.
Each answer is tied to the VSEPR theory, which helps predict the shapes of molecules based on the repulsion between electron pairs around a central atom. This method considers both bonding and lone pairs to determine the most stable arrangement of atoms.
