Anomalous Properties of the First Elements of the Group

The primary groups or representative elements that make up s-block and p-block are referred to as key groups or representative elements. The p-block atoms are smaller than their neighbouring s or d block atoms because the atomic radii decrease over time. As a result, the radius of the F atom is the smallest.The high electronegativity ratings of N, O, and F are due to their small size. The development of rather strong hydrogen bonds reflects this. Carbon, nitrogen, and oxygen are distinguished from other elements in their groups by their capacity to form p–p multiple bonds. Because the atomic orbitals (3p) are too broad to accomplish effective overlapping, later members such as Si, P, S, and others do not form p–p bonds. In the second period, the valence shell capacity of the p-block components limits the coordination number to a maximum of four. Higher coordination numbers are possible in compounds with heavier components.

Large charge to radius ratio

The atomic radii are reduced as you move over the era. As a result, the elements of the p block are smaller than those of the s and d blocks. Fluorine atoms have the shortest radius. Fluorine, nitrogen, and oxygen have substantially greater electronegativities due to their short size. It’s also reflected in the fact that they create stronger hydrogen bonds than other elements.In comparison to other members of the groups, the first member of the p block elements has a stronger potential to form pi-pi connections with itself and other elements of the second period, which accounts for the greater disparities.This is owing to the fact that the heavier p orbitals are broad and diffused, making effective sideway overlapping impossible. Nitrogen, carbon, and oxygen are distinct from the other elements in their respective groups in that they have the unique potential to form numerous bonds, specifically p–p, due to the fact that their atomic orbitals are far too big to achieve effective overlapping.

Unavailability of vacant d orbitals

The four valence orbitals of the first element in the p block elements, one of which is 2s and the other three of which are 2p, limit the maximum covalency of the first element in each group to four. Because there are unoccupied d orbitals in the valence shells of the other p block components, they have a covalency of more than four. The pentoxides can be formed by nitrogen, but not the pentachloride. The coordination number is limited to four due to their valency; however, the heavier members’ compounds can have a greater coordination number.

Valence shell and high electronegativity

When the initial elements are bound to hydrogen atoms, they form intermolecular hydrogen bonds that are stronger than any other intermolecular forces due to their high electronegativity and tiny size, as well as the presence of ion pairs of electrons. As a result, the compounds of the first element of each group in the p block elements have high melting and boiling points.The other members of the group are solids, except for oxygen, which is a diatomic gas. It has a significant non-metallic content. The oxygen molecule is paramagnetic in nature, whereas the molecules of the other elements are diamagnetic. Nitrogen is a gas, while the rest of its family consists of solids.

The nitrogen molecule is diatomic, but the molecules of the other parts are triatomic, allowing it to form tri negative ions. Nitrogen hydrides are more stable than the other hydrides in the category. The fluorine gas is the most reactive of all the halogens. It only shows the negative oxidation state, while the other elements in this group have positive oxidation states.

Anomalous behaviour of lithium and boron and beryllium

Lithium is harder than the other metals in its group. Its melting and boiling points are higher than those of other metals. It has the least amount of reactivity. Other alkali metal ions normally form anhydrous salts as the polarising power of the ions decreases with increasing ion size.

Boron, the first of the group 13 elements, has peculiar characteristics that set it apart from the rest of its family. The following are the key reasons behind the disparity: 

1. Boron is more difficult than the other members of its group due to its modest size. 
2. Its melting and boiling points are higher than those of the other members of its family.

Beryllium, the first element in group 2, has various features that set it apart from the other elements in its group, resulting in unusual behaviour. Beryllium’s unusual behaviour is caused by the following factors:

• All other alkaline earth metal atoms are smaller than it.
• It has the highest ionisation energy of all the elements.
• Beryllium’s electronegativity is higher than that of other elements.
• In its valence shell, there are no unoccupied d-orbitals.

Beryllium compounds are typically covalent due to their higher electronegativity. This is due to the fact that when Beryllium combines with another element, the difference in electronegativity between the two elements is usually small.

Conclusion

People and things both have anomalies, and elements in the periodic table have anomalies as well. In simple words, anomaly can be defined as a difference in behaviour when compared to other members of a group. The identity element E, which differs from the others because it is its own inverse, is usually regarded as the first element in a group. The inverse of an element belongs to the same class as the element.