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Bond parameters deal with the characterization of covalent bonds based on various parameters such as bond angle, bond enthalpy, bond length, etc. The bond parameters provide comprehension of the stability of chemical compounds and the strength of the chemical bonds holding its atoms together.
Key Terms: Bond Order, Ionic Bond, Covalent Bond, Spectroscopy, Electron Diffraction, Bond Dissociation Energy
Chemical Bonding
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Covalent bonds are characterized based on several bond parameters such as bond length, bond angle, bond energy (Bond enthalpy), and bond order. Different atoms combine together to become stable. The combination takes place by forming bonds. The different types of bonding are ionic, covalent and metallic. This indicates that each bond has some features associated with it. The electronegativity disparity of the atoms participating in the chemical bond contributes to the bond energy.
Bond Length
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Bond length, also referred to as bond distance, is the equilibrium internuclear separation length of the bonded atoms in a molecule. It is measured by rotational spectroscopy, electron diffraction and X-ray diffraction techniques. In a covalent bond, the contribution from each atom is known as the covalent radius of that atom. The bond lengths are directly proportional to the atomic radii of the participating atoms.
Bond Length
Bond Angle
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Bond angle is the angle shaped between two covalent bonds that arise from the same atom. It is considered the geometric angle between two adjacent bonds. The geometry of a molecule can be described using bond angles and distances.
Bond Angle
Bond Order
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In covalent bond, the bond order is the overall covalently bonded electron pairs between two atoms in a molecule. It indicates the stability of a chemical bond. The higher the bond order, the stronger the chemical bond.
Bond order = (number of bonding electrons - number of antibonding electrons)/ 2
If bond order = 0,that means the two atoms are not bonded. A compound can have a bond order of zero, this value is not possible for elements.
- Single bonds consist of a bond order of 1.
- Double bonds - bond order 2
- Triple bonds - bond order 3
Bond Enthalpy
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Bond enthalpy is the measure of the energy of a chemical bond. It is considered as the strength required to break all covalent bonds of a certain type in one mole of a chemical compound. The bond energy and bond dissociation energy are different. The latter is the shift in enthalpy related to the homolytic cleavage of a bond. Whereas the former is the average bond dissociation enthalpies of all bonds in a specific molecule. Some of the characteristics affecting the bond energy are:
- Bond energy is inversely proportional to the length of the bond. The longer the bonds, the lesser the bond energy.
- Bond energy is directly proportional to the bond order. Multiple bonds possess higher bond energy.
- Bond energy is inversely proportional to the atomic radii of the atoms participating in the bond.
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Things to Remember
- Bond parameters deal with the characterization of covalent bonds on the basis of different parameters lik bond enthalpy/ energy, bond angle, bond length, etc.
- The bond length is determined as the equilibrium internuclear separation distance of the bonded atoms in a molecule.
- The parameters provide an insight into the stability of chemical compounds and the strength of the chemical bonds holding its atoms together.
- Bond enthalpy is the energy required to break a specific bond in one mole of a gaseous molecule.
Sample Questions
Ques: Define the enthalpy of bond dissociation? (2 marks)
Ans: Bond enthalpy is the energy contained in a bond between atoms in a molecule. It is also known as bond strength, average bond energy or bond-dissociation enthalpy.
Ques: Explain bond angle? And state the strongest bond? (2 marks)
Ans: Bond angle is the arc formed between three atoms over two bonds. It is the geometry angle between two adjacent covalent bonds. The triple bonds between two similar atoms are stronger than the double bonds.
Ques: Are polar bonds stronger? (2 marks)
Ans: The polar bonds are stronger due to the coulomb forces involved. They are soluble in water, hence it can be quickly dissolved. At the same time, nonpolar bonds cannot be dissolved quickly.
Ques: What are bond parameters? (2 marks)
Ans: Bond parameters refer to the classification of covalent bonds based on different parameters like bond angle, bond length, bond enthalpy, and bond order.
Ques: Compare Valence Bond Theory and Molecular Orbital Theory. (2 marks)
Ans: Both the theories involve distribution of electrons. In Valence Bond Theory, the bonds are localized into two atoms only. In Molecular Orbital Theory, bonds are localized in atoms as well as molecule. Resonance is very important in VBT, but not significant in Molecular Orbital Theory. The calculations are simpler in VBT and tedious in MOT.
Ques: What are the types of bond parameters? (2 marks)
Ans: Generally, there are three different types of chemical bonds. They are covalent, coordinate, and ionic or electrovalent bonds. All bonds consist of some characteristics associated with it called bond parameters.
Ques: Is double bond stronger than triple bond? (2 marks)
Ans: Considering the presence of two pi bonds, triple bonds are much stronger than double bonds. Every carbon consists of two hybrid sp-orbitals and one of them overlaps to shape an sp-sp sigma bond using the matching one from the other carbon atom.
Ques: Explain bond length? (2 marks)
Ans: Bond length or bond distance is the equilibrium internuclear separation distance of the bonded atoms in a molecule. The bond length is measured using rotational spectroscopy, X-ray diffraction techniques, and electron diffraction. Here, the bond lengths are directly proportional to the atomic radii of the participating atoms.
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