Chemical Bonding — Molecular Geometry and Hybridization: Identify Central Atom Hybridization

Question 

Identify the hybridization of the central atom in each of the following molecules and ions that contain multiple bonds:

  1. CS2
  2. Cl2CO (C is the central atom)
  3. Cl2SO (S is the central atom)
  4. SO2F2 (S is the central atom)
  5. XeO2F2 (Xe is the central atom)

 

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  1. sp
  2. sp2
  3. sp3
  4. sp3
  5. sp3d

Refer to Section 5.3: Hybrid Atomic Orbitals (1).

Strategy Map

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Table 1: Strategy Map
Strategy Map Steps
1. Create a Lewis structure of the molecule.

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Refer to Section 4.4: Lewis Symblos and Structures (2).
2. Determine the electron-pair geometry of the molecule.

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Recall using VSEPR to determine electron-pair geometry.

Refer to Section 5.1: Molecular Structure Polarity (3).
3. Identify the hybridization of the centre atom based on the molecules’ electron-pair geometry.

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The hybridization of the centre atom will be determined by the electron-pair geometry, not the atom itself. For example, in a linear molecule, the centre atoms hybridization will always be sp.

Solution

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1. CS2

16 valence electrons, C central atom

There are two structures indicated separated by a forward slash line. To the left, the central atom "C" is connected to the letters "S" on both sides by two horizontal lines. Each letter "S" has two pairs of filled dots and each pair has two filled dots. To the right, the central atom C is connected to the letters S on both sides by two horizontal lines.

Answer: This molecule has a linear electron-pair geometry; sp hybridized (s + p)

2. Cl2CO (C is the central atom)

24 valence electrons

There are two structures indicated separated by a forward slash line. The image on the left has the central atom "C" connected to the letters "Cl" on the left and right by a straight line. Each "Cl" has three pairs of filled dots around it. Above the central atom C, the letter "O" is connected by two horizontal lines . The letter O has two pairs of filled dots above it. The image on the right has the central atom C connected to the letter O directly above it by two horizontal lines. To the right and left of C are the letters "Cl" connected by horizontal lines.

Answer: This molecule has a trigonal planar electron-pair geometry; sp2 hybridized (s + p + p)

3.Cl2SO (S is the central atom)

26 valence electrons

There are two structures indicated separated by a forward slash line. The image on the left has the central atom "S" with two filed dots directly above it. To the left and directly below the central atom, the letters "Cl" are connected by a straight line. Each Cl has three pairs of filled dots around it. To the right of the central atom, the letter "O" is connected by two horizontal lines. Two pairs of filled dots are on the letter O. The image on the right has the central atom S with two filled dots above it. To the right of the central atom, the letter O is connected by two horizontal lines. To the left of the central atom, the letters "Cl" are connected by a diagonal line. Below the central atom the letters "Cl" are connected by a solid filled triangle.

Answer: This molecule has a tetrahedral electron-pair geometry; sp3 hybridized (s + p + p + p)

4. SO2F2 (S is the central atom)

32 valence electrons

There are two structures indicated separated by a forward slash line, The image on the left has a central atom "S" connected to the letter "O" above it by two horizontal lines. To the right of the central atom, the letter "O" is connected by two horizontal lines. To the left and bottom, the letter "F" is connected to the cental atom by a horizontal line. Each of the letters "F" have three pairs of filled dots around it and the letters "O" have two pairs of filled dots around it. The image on the right has a central atom "S" connected to the letter "O" to the right by two horizontal lines and the letter "O" directly above it by two horizontal lines. To the left of "S", the letter "F" is connected by a diagonal line and below "S", the letter "F" is connected by a solid filled triangle.

Answer: This molecule has a tetrahedral electron-pair geometry; sp3 hybridized (s + p + p + p)

5. XeO2F2 (Xe is the central atom)

34 valence electrons

There are two structures indicated separated by a forward slash line. The image on the left has a central atom "Xe". To the left of the central atom is the letter "F" connected by a straight line. To the right, is the letter "O" connected by a line. Above the central atom is the letter "F" connected by a line. Below the central atom is the letter "O" connected by a line. The letters "F" and "O" each have three pairs of filled dots around it. The central atom "Xe" has two filled dots above it. The image on the right has a central atom "Xe". Above and below the central atom is the letter "F" connected by a straight line. To the top right of the central atom is the letter "O" connected by a diagonal line. To the bottom right of the central atom is the letter "O" connected by a solid filled triangle. The central atom "Xe" has two filled dots to the left of it.

Answer: This molecule has a trigonal bipyramidal electron-pair geometry; sp3d hybridized (s + p + p + p + d)

Guided Solution

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The guided solution below will give you the reasoning for each step to get your answer, with reminders and hints.

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Table 2: Guided Solution
Guided Solution Ideas
This question is a theory problem where you use your knowledge of molecular bonding and identify atomic orbital hybridization.

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Refer to Section 5.3 Hybrid Atomic Orbitals (1).
What is the pattern associated with atomic orbital hybridization?

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The hybridization of the centre atom will be determined by the electron-pair geometry, not the atom itself. For example, the centre atoms hybridization will always be sp in a linear molecule.

Number of electron domains (as determined by the number of bonding directions and lone pairs in the best Lewis structure) = Number of atomic orbitals required for hybridization.

Number of hybrid orbitals = Number of orbitals mixed.

Hybrid orbitals are named by type and number of orbitals mixed.

Show/Hide Don’t Forget!

Recall the atomic orbitals: for n = 2 there is 1 ‘s’ orbital (l = 0) and 3 degenerate ‘p’ orbitals (l = 1).

Note that ‘d’ orbitals (l = 2) can only exist when n is greater than or equal to 3.

  • 2 domains = 2 atomic orbitals must be hybridized = s + p = sp hybridization = linear electron domain geometry (EDG)
  • 3 domains = 3 atomic orbitals must be hybridized = s + p + p = sp2 hybridization = trigonal planar EDG
  • 4 domains = 4 atomic orbitals must be hybridized = s + p + p + p = sp3 hybridization = tetrahedral EDG
  • 5 domains = 5 atomic orbitals must be hybridized = s + p + p + p + d = sp3d hybridization = trigonal bipyramidal EDG
  • 6 domains = 6 atomic orbitals must be hybridized = s + p + p + p + d + d = sp3d2 hybridization = octahedral EDG
Table 3: Complete Solution
Complete Solution
a. CS2

16 valence electrons, C central atom

There are two structures indicated separated by a forward slash line. To the left, the central atom "C" is connected to the letters "S" on both sides by two horizontal lines. Each letter "S" has two pairs of filled dots and each pair has two filled dots. To the right, the central atom C is connected to the letters S on both sides by two horizontal lines.

 

Answer: This molecule has a linear electron-pair geometry; sp hybridized (s + p)
b. Cl2CO (C is the central atom)

24 valence electrons

 

There are two structures indicated separated by a forward slash line. The image on the left has the central atom "C" connected to the letters "Cl" on the left and right by a straight line. Each "Cl" has three pairs of filled dots around it. Above the central atom C, the letter "O" is connected by two horizontal lines . The letter O has two pairs of filled dots above it. The image on the right has the central atom C connected to the letter O directly above it by two horizontal lines. To the right and left of C are the letters "Cl" connected by horizontal lines.

 

Answer: This molecule has a trigonal planar electron-pair geometry; sp2 hybridized (s + p + p)
c. Cl2SO (S is the central atom)

26 valence electrons

 

There are two structures indicated separated by a forward slash line. The image on the left has the central atom "S" with two filed dots directly above it. To the left and directly below the central atom, the letters "Cl" are connected by a straight line. Each Cl has three pairs of filled dots around it. To the right of the central atom, the letter "O" is connected by two horizontal lines. Two pairs of filled dots are on the letter O. The image on the right has the central atom S with two filled dots above it. To the right of the central atom, the letter O is connected by two horizontal lines. To the left of the central atom, the letters "Cl" are connected by a diagonal line. Below the central atom the letters "Cl" are connected by a solid filled triangle.

 

Answer: This molecule has a tetrahedral electron-pair geometry; sp3 hybridized (s + p + p + p)
d. SO2F2 (S is the central atom)

32 valence electrons

 

There are two structures indicated separated by a forward slash line. The image on the left has a central atom "S" connected to the letter "O" above it by two horizontal lines. To the right of the central atom, the letter "O" is connected by two horizontal lines. To the left and bottom, the letter "F" is connected to the cental atom by a horizontal line. Each of the letters "F" have three pairs of filled dots around it and the letters "O" have two pairs of filled dots around it. The image on the right has a central atom "S" connected to the letter "O" to the right by two horizontal lines and the letter "O" directly above it by two horizontal lines. To the left of "S", the letter "F" is connected by a diagonal line and below "S", the letter "F" is connected by a solid filled triangle.

 

Answer: This molecule has a tetrahedral electron-pair geometry; sp3 hybridized (s + p + p + p)
e. XeO2F2 (Xe is the central atom)

34 valence electrons

 

There are two structures indicated separated by a forward slash line. The image on the left has a central atom "Xe". To the left of the central atom is the letter "F" connected by a straight line. To the right, is the letter "O" connected by a line. Above the central atom is the letter "F" connected by a line. Below the central atom is the letter "O" connected by a line. The letters "F" and "O" each have three pairs of filled dots around it. The central atom "Xe" has two filled dots above it. The image on the right has a central atom "Xe". Above and below the central atom is the letter "F" connected by a straight line. To the top right of the central atom is the letter "O" connected by a diagonal line. To the bottom right of the central atom is the letter "O" connected by a solid filled triangle. The central atom "Xe" has two filled dots to the left of it.

 

Answer: This molecule has a trigonal bipyramidal electron-pair geometry; sp3d hybridized (s + p + p + p + d)

Check Your Work

Verify that:

  • Your Lewis structure has all the valence electrons.
  • You have counted the central atom’s electron domains correctly.

The name of our electron pair geometry and number of electron domains leads us to the correct hybridization.

Does your answer make chemical sense?

Show/Hide Answer

Hybrid orbitals form due to the covalent bonding within molecules. When 2 or more atoms create a covalent bond, their atomic orbitals will overlap to form these hybrid orbitals.

In this case, we are looking at the hybridization of the centre atom to see what kind of hybridization is happening to overlap with all the atoms. When molecules grow and involve more atoms, more bonds form, and thus, more orbitals become involved. This is why a linear molecule only uses 2 orbitals (s + p), while an octahedral molecule uses 6 (s + p + p + p + d + d).

PASS Attribution

References

1. OpenStax. 5.3: Hybrid Atomic Orbitals. In CHEM 1500: Chemical Bonding and Organic Chemistry; LibreTexts, 2022. https://chem.libretexts.org/Courses/Thompson_Rivers_University/CHEM1500:_Chemical_Bonding_and_Organic_Chemistry/05:_Chemical_Bonding_II-_Molecular_Geometry_and_Hybridization_of_Atomic_Orbitals/5.03:_Hybrid_Atomic_Orbitals.

2. OpenStax. 4.4: Lewis Symbols and Structures. In General Chemistry 1; LibreTexts, 2020. https://chem.libretexts.org/Courses/Nassau_Community_College/General_Chemistry_1/04%3A_Chemical_Bonding_and_Molecular_Geometry/4.04%3A_Lewis_Symbols_and_Structures.

3. OpenStax. 5.1: Molecular Structure and Polarity. In CHEM 1500: Chemical Bonding and Organic Chemistry; LibreTexts, 2022. https://chem.libretexts.org/Courses/Thompson_Rivers_University/CHEM1500%3A_Chemical_Bonding_and_Organic_Chemistry/05%3A_Chemical_Bonding_II-_Molecular_Geometry_and_Hybridization_of_Atomic_Orbitals/5.01%3A_Molecular_Structure_and_Polarity.

4. Blackstock, L.; Brewer, S.; Jensen, A. PASS Chemistry Book CHEM 1500; LibreTexts, 2023. https://chem.libretexts.org/Courses/Thompson_Rivers_University/PASS_Chemistry_Book_CHEM_1500.

5. Blackstock, L.; Brewer, S.; Jensen, A. 5.3: Question 5.E.59 PASS – Identify Central Atom Hybridization. In PASS Chemistry Book CHEM 1500; LibreTexts, 2023. https://chem.libretexts.org/Courses/Thompson_Rivers_University/PASS_Chemistry_Book_CHEM_1500/05%3A_Chemical_Bonding_II_-_Molecular_Geometry_and_Hybridization_of_Atomic_Orbitals/5.03%3A_Question_5.E.59_PASS_-_identify_central_atom_hybridization.

6. OpenStax. 8.E: Advanced Theories of Covalent Bonding (Exercises). In Chemistry 1e (OpenSTAX); LibreTexts, 2022. https://chem.libretexts.org/Bookshelves/General_Chemistry/Chemistry_1e_(OpenSTAX)/08%3A_Advanced_Theories_of_Covalent_Bonding/8.E%3A_Advanced_Theories_of_Covalent_Bonding_(Exercises).

7. Flowers, P.; Robinson, W. R.; Langley, R.; Theopold, K. Ch. 8 Exercises. In Chemistry; OpenStax, 2015. https://openstax.org/books/chemistry/pages/8-exercises.

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