INTRODUCTION TO BOND PARAMETERS – Bond length, Bond angle, Bond enthalpy and Bond order
Atoms combine together to become stable. The combination takes place by forming bonds. There are different types of bond viz. ionic or electrovalent bond, covalent bond and coordinate bond. Every bond has some feature associated with it. This article discusses the different features or characteristics of bonds which can also be called as bond parameters.
- Bond length is defined as the distance between the centres of the nuclei of two bonded atoms in equilibrium position.
- Stronger the force of attraction between the bonding atoms, smaller the bond length.
- Bigger the size of atom, longer the bond length.
- It is measured by spectroscopic, X-ray diffraction and electron diffraction technique.
- Each atom of the bonded pair contributes to the bond length.
- In case of covalent bond, the contribution by each atom is called covalent radius of that atom.
- Bond angle is defined as the angle between the two bonds i.e. angle between two orbitals containing bonding electron pairs around the central atom in a complex molecule or an ion.
- It is measured in degrees and is calculated using spectroscopic method.
- It gives the idea about the distribution of bonded electron pairs around the atoms.
- It helps in the determination of shape of the molecules.
- It is defined as the amount of energy required to break one mole of the bond of particular type between two atoms in gaseous states.
- Bond enthalpy is directly proportional to the strength of the bond between the molecules.
- In polyatomic molecules, the two bonds of the same type can have different bond enthalpy.
For e.g.: Two O-H bonds of water molecule have different bond enthalpy.
- Due to differences in bond enthalpy, polyatomic molecules have average bond enthalpy.
- It is the number of bonds formed between the two atoms in a molecule. This definition is according to the Lewis description of covalent bonds.
- Isoelectronic molecules or ions have same bond order.
For e.g. F2 and O22- are isoelectronic molecules and so have same bond order of 1.
- Greater the bond order, bond enthalpy increases and bond length decreases.
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