Question

How would you expect the extent of overlap of atomic orbitals to vary in the series IF, ICl, \(\mathrm{IBr}\), and \(\mathrm{I}_{2}\) ?

Short answer

The extent of overlap in atomic orbitals is expected to decrease as the atomic size of the halogens increases across the given series, IF, ICl, \(\mathrm{IBr}\), and \(\mathrm{I}_{2}\). This is because larger orbitals have less significant overlap, resulting in weaker bonds. Therefore, the overlap will vary in the order: IF > ICl > \(\mathrm{IBr}\) > \(\mathrm{I}_{2}\).

Step-by-step solution

Understanding atomic orbital overlap

Atomic orbital overlap refers to the degree to which two atoms share their electron clouds when forming a bond. This overlap is the foundation of covalent bonding, where electrons are shared between two atoms. Generally, greater overlap between atomic orbitals results in a stronger and shorter bond.

Understanding the trend in atomic size

As we move down a group in the periodic table, the atomic size increases. This is because electrons are added to higher energy levels, which are further from the nucleus. Consequently, the size of the orbitals also increases. In the given series, the atoms bonded to iodine belong to Group 17 (halogens). Going down the group, we have fluorine (F), chlorine (Cl), and bromine (Br).

Analyzing the effect of atomic size on overlap

As the size of an atomic orbital increases, the area where an effective overlap can occur decreases. When an atom has a larger orbital, it is more difficult for another atom's orbital to have a significant overlap with it. Therefore, the larger the orbitals, the less likely they are to overlap significantly, resulting in a weaker bond.

Applying the trends to the given series

As we go through the series IF, ICl, \(\mathrm{IBr}\), and \(\mathrm{I}_{2}\), the atomic size of the halogens increases. This means that the size of their orbitals also increases. Since larger orbitals have less significant overlap with each other, we can expect the extent of overlap to decrease as we go through the series. So, the extent of overlap in atomic orbitals is expected to be greatest for IF and least for \(\mathrm{I}_{2}\). It will vary in the order: IF > ICl > \(\mathrm{IBr}\) > \(\mathrm{I}_{2}\).