EQB9: Molecular Geometry

The angle between the hydrogen atoms in water (H2O) is slightly less than expected for a tetrahedral shape. This is because of the

• extra electron repulsion from the lone pairs.
• atomic radius of the oxygen atom.
• additional repulsion of the shared electrons.
• extra repulsion of the hydrogen atoms.

Answer explanation

- **Explanation**: Water molecules have two lone pairs on the oxygen atom, which exert more repulsion than bonding pairs, reducing the H-O-H angle from the tetrahedral angle (109.5°) to about 104.5°.

Which hybrid orbitals would be formed if one s orbital and three p orbitals combined?

• sp
• sp2
• sp3
• sp4

Answer explanation

- **Explanation**: Combining one s orbital with three p orbitals results in sp3 hybridization, characteristic of tetrahedral molecules like methane (CH4).

The boron atom of BBr3 has

• one atomic orbital.
• two atomic orbitals.
• three hybrid orbitals.
• four hybrid orbitals.

Answer explanation

- **Explanation**: BBr3's boron atom undergoes sp2 hybridization to form three sp2 hybrid orbitals, aligning in a trigonal planar shape for bromine bonding.

Which statement describes a molecule that has a trigonal pyramidal molecular shape?

• The molecule has a trigonal planar electron domain geometry with one lone pair.
• The molecule has a tetrahedral electron domain geometry with one lone pair.
• The molecule has a trigonal planar electron domain geometry with two lone pairs.
• The molecule has a tetrahedral electron domain geometry with two lone pairs.

Answer explanation

- **Explanation**: A trigonal pyramidal shape indicates a central atom with three bonded atoms and one lone pair, as seen in NH3, distorting the tetrahedral geometry.

How many hybrid orbitals are found in CCl4?

• one
• two
• three
• four

Answer explanation

- **Explanation**: CCl4 has a central carbon atom with sp3 hybridization, forming four hybrid orbitals that bond with four chlorine atoms in a tetrahedral geometry.

The figure shows the hybrid orbitals of methane. Which molecule has the same shape and hybridization as methane?

• SO3
• C2H2
• CH2O
• CF2Cl2

Answer explanation

- **Explanation**: Like methane, CF2Cl2 has a tetrahedral shape and sp3 hybridization, with the central carbon atom bonding to four other atoms.

Tags

NGSS.HS-PS1-1

Consider the Lewis dot structures below, which represent the valence electrons of carbon (C) and chlorine (Cl). When these bond to make CCl4, what is the shape of a CCl4 molecule?

• linear
• circular
• tetrahedral
• trigonal planar

Answer explanation

- **Explanation**: CCl4's Lewis structure, with a central carbon atom bonded to four chlorine atoms, results in a tetrahedral shape due to sp3 hybridization.

Which molecule has a trigonal planar shape?

• carbon monoxide
• boron trichloride
• silicon tetraiodide
• carbon tetrafluoride

Answer explanation

- **Explanation**: BF3 has a trigonal planar shape due to sp2 hybridization of the boron atom, bonding with three fluorine atoms in a flat geometry.

A molecule has two atoms that are bonded to the central atom and one lone pair of electrons around this central atom. What is the shape of the molecule?

• bent
• linear
• trigonal planar
• trigonal pyramidal

Answer explanation

- **Explanation**: With two bonded atoms and one lone pair on the central atom, the shape is bent, as lone pairs repel more strongly, altering linear geometry.

The shape of a molecule is trigonal planar. How many electron domains around the central atom does this molecule most likely have?

• zero
• two
• three
• four

Answer explanation

- **Explanation**: Trigonal planar molecules have three electron domains (three bonding pairs) around the central atom, with no lone pairs.