Bond Order - UNSOLVED PRACTICE SET
Chapter: Chemical Bonding and Molecular Structure | Topic: Bond Order
BOND ORDER - UNSOLVED PRACTICE SET
Topic: Bond Order
Multiple Choice Questions
Q1. Bond order is defined as:
- The total number of bonds between two atoms
- Half the difference between the number of bonding and antibonding electrons
- The energy required to break a bond
- The length of a bond
Q2. A bond order of zero means:
- A very strong bond
- A very weak bond
- No bond exists between the atoms
- A coordinate bond
Q3. The bond order of N₂ is:
- 1
- 2
- 3
- 4
Q4. If a species has a bond order of 1.5, it indicates:
- A single bond
- A double bond
- A bond intermediate between single and double
- No bond
Q5. The bond order of O₂⁺ compared to O₂ is:
- Lower
- Higher
- The same
- Zero
Q6. Which of the following has the highest bond order?
- O₂
- O₂⁺
- O₂⁻
- O₂²⁻
Short Answer Questions
Q7. Define bond order. How is it related to bond strength and bond length?
Q8. Calculate the bond order of O₂ using molecular orbital theory. Is O₂ paramagnetic or diamagnetic?
Q9. Why does N₂ have a higher bond order than O₂? What does this imply about their relative stability?
Q10. The bond order of NO is 2.5. Explain what a fractional bond order means in terms of molecular stability.
Q11. Your friend tells you that her relationship with her study partner is "2.5 out of 3" — stronger than a casual friendship (1) but not as committed as best friends (3). How is this exactly analogous to the bond order in NO, where the fractional value indicates a bond strength between a double bond and a triple bond?
Q12. Arrange the following in order of increasing bond order: O₂, O₂⁺, O₂⁻, O₂²⁻. Explain your reasoning.
Long Answer Questions
Q13. Explain the concept of bond order. How is it calculated using Molecular Orbital Theory? Discuss the relationship between bond order and:
(a) Bond length
(b) Bond energy
(c) Magnetic properties
Illustrate with the examples of N₂, O₂, and F₂.
Q14. Describe how bond order helps predict the stability and properties of molecular species. For the following species, calculate bond order and predict stability:
(a) H₂
(b) He₂
(c) Li₂
(d) Be₂
Why does He₂ not exist as a stable molecule while He₂⁺ does?
Q15. During a chemistry olympiad, you encounter the following problem:
(a) The bond order of CO is 3, the same as N₂. Yet CO is polar while N₂ is non-polar. Explain why bond order alone cannot predict molecular polarity.
(b) The superoxide ion O₂⁻ has a bond order of 1.5. Draw its MO configuration and show the calculation.
(c) The peroxide ion O₂²⁻ has a bond order of 1.0. Compare its bond length with O₂ (bond order 2) and explain.
(d) A mystery diatomic species has a bond order of 2.5 and is paramagnetic. Identify the species and write its MO configuration.
Numerical / Application-Based Problems
Q16. Calculate the bond order for the following species using molecular orbital theory. Show your calculations and predict magnetic behaviour:
(a) N₂
(b) N₂⁺
(c) N₂⁻
(d) O₂²⁻
Q17. The following table gives information about diatomic species of the second period:
| Species | Total Electrons | Bond Order | Bond Length (pm) | Magnetic Nature |
|---|---|---|---|---|
| Li₂ | 6 | ? | 267 | ? |
| B₂ | 10 | ? | 159 | ? |
| C₂ | 12 | ? | 124 | ? |
| N₂ | 14 | ? | 110 | ? |
| O₂ | 16 | ? | 121 | ? |
| F₂ | 18 | ? | 142 | ? |
(a) Complete the table by calculating bond order and predicting magnetic nature.
(b) Plot a graph of bond order vs. bond length for these species. What trend do you observe?
(c) N₂ has the shortest bond length despite O₂ having a lower bond order than expected. Explain this anomaly.
(d) Predict the bond order and bond length of Ne₂. Does it exist?
Q18. Consider the following diatomic species and their ions:
(a) For the species CN, CO, and NO⁺ (all 14-electron species):
(i) Write the MO configuration for each.
(ii) Calculate the bond order.
(iii) Predict which has the highest bond dissociation energy.
(b) The species NO has 15 electrons. Compare its bond order with NO⁺ and NO⁻.
(c) Explain why isoelectronic species (same number of electrons) tend to have similar bond orders but may differ in other properties.