The majority of the trends in chemical properties of elements, such as diagonal relationships, inert pair effect, effects of lanthanoid contraction, and so on, will be reasonable for abnormal behaviour. Anomalous combinations are elements that do not follow the increasing order of atomic masses. Mendeleev arranged these elements according to similarity rather than increasing the order of atomic mass. An element’s abnormal behaviour is defined as its distinct behaviour in comparison to other elements in the same group. It has anomalous properties due to its one-of-a-kind characteristics. Lithium and beryllium, for example, form more covalent compounds than alkali and alkali earth metals, which primarily form ionic compounds. The elements of the second period have only four orbitals (2s and 2p) in the valence shell and a maximum co-valence of four, whereas the members of the subsequent periods have more orbitals in their valence shell and higher valences.
In general, anomalous pairs are elements that do not follow the increasing order of atomic masses. Mendeleev formulated these elements in ascending order of atomic mass rather than similarity. The first element in a group exhibits unusual behaviour due to its small size, large (charge/radius) ratio, high ionisation enthalpy, high electronegativity, and lack of d-orbitals in its valance shell. The primary reason for displaying anomalous properties of the first member of a group in a s or p-block is the proclivity to form multiple bonds. Be is an alkaline earth metal that exhibits anomalous behaviour and has the same electronegativity as aluminium. Be and Al are diagonally related. Be and Al exhibit unusual behaviour due to their high ionisation energy and the fact that they have small atomic and ionic sizes.
Hydrogen is the most abundant element in the universe and highly flammable gas. It is the lightest element ever discovered, with no colour, odour, or taste. It can also be found in the majority of organic compounds. Hydrogen is considered the first element in the periodic table. Hydrogen is the most basic atom.Hydrogen is used in the chemical industry to produce ammonia for agricultural fertiliser (the Haber process), as well as cyclohexane and methanol. It is found in water and almost all living things’ molecules. The majority of hydrogen is created by combining natural gas and steam to create syngas (a mixture of hydrogen and carbon monoxide).
The hydrogen is extracted from the syngas. It can also be produced through a process known as electrolysis. It has a single proton in its nucleus, which is orbited by a single electron. It is the only element that is devoid of neutrons. Hydrogen has an atomic weight of 1.0079. The density of liquid hydrogen is the lowest of any liquid, while the density of crystalline hydrogen is the lowest of any crystalline solid. It combines violently with the elements oxygen, chlorine, and fluorine.
Polonium (Po), is a radioactive, silvery-gray, or black metallic oxygen group element (Group 16 [VIa] in the periodic table). Polonium, the first element discovered by radiochemical analysis, was discovered in 1898 by Pierre and Marie Curie, who was investigating the radioactivity of a specific pitchblende, a uranium ore. The extremely intense radioactivity that could not be attributed to uranium was attributed to a new element, which they named after Marie Curie’s homeland, Poland. The discovery was made public in July 1898.
In general, polonium is said to be relatively rare, even in pitchblende: 1,000 tonnes of ore must be processed in order to obtain 40 milligrams of polonium. It is found in about one part in 1015 of the Earth’s crust. It occurs naturally as a by-product of the radioactive decay of uranium, thorium, and actinium. The half-lives of its isotopes range from a fraction of a second to 103 years; polonium-210, the most common natural isotope, has a half-life of 138.4 days.
Polonium is typically isolated from by-products of radium extraction from uranium minerals. Pitchblende ore is treated with hydrochloric acid, and the resulting solution is heated with hydrogen sulphide to precipitate polonium monosulfide, PoS, as well as other metal sulphides, such as bismuth, which chemically resembles polonium monosulfide but is less soluble.
Due to the obvious difference in solubility, repeated partial precipitation of the sulphide mixture concentrates polonium in the more soluble fraction while bismuth accumulates in the less soluble portions. However, the difference in solubility is minor, and the process must be repeated several times to achieve complete separation. An electrolytic deposition is used to purify the water. It can be synthesized by bombarding bismuth or lead with neutrons or accelerated charged particles.
Since polonium is highly radioactive, it must be handled with extreme caution because it disintegrates to a stable isotope of lead by emitting alpha rays, which are streams of positively charged particles. Polonium is used in industry to eliminate static electricity generated by processes such as paper rolling, the manufacture of sheet plastics, and the spinning of synthetic fibres when it is contained in substances such as gold foil, which prevents alpha radiation from escaping.
The first element among all groups exhibits abnormal behaviour for the following reasons:
High Electronegativity: The electronegativity of an element decreases as it progresses through the group. As a result, the first element of a group has a higher electronegative charge.
Small Size: The addition of new shells increases the size of an atom as it moves down the group. Smaller atoms react differently than larger atoms.
Absence of d-orbitals: The first period elements do not have d-orbitals. Because of this, they cannot expand their valency like their subsequent group members.
The anomalous behaviour of the first element of each group’s s and p block elements in comparison to other group members is due to many reasons such as the atoms with a very small size, a high charge/radius ratio, high electronegativity, and no d-orbitals in their valence shell.
When compared to other members of the groups, the first member in the groups of the p block elements has a greater ability to form pi-pi bonds with itself and other elements of the second period, which accounts for the greater differences. This is because the heavier s p orbitals are large and diffused, making effective sideway overlapping impossible. Nitrogen, carbon, and oxygen are significantly different from the other elements in their respective groups because they have the unique ability to form multiple bonds, specifically p–p, due to their atomic orbitals being far too large for effective overlapping.
Because of their high electronegativity and small size, as well as the presence of electron-ion pairs, the first elements form intermolecular hydrogen bonds, which are stronger than any other intermolecular force. It causes the compounds of the first element of each group in the p block elements to have high melting and boiling points.
Also read: Anomalous Properties of Boron Hydrides
Nitrogen is tiny, strongly electronegative, and also has high ionization energy, and the absence of valence electrons in d orbital oxygen indicates abnormal behaviour. Nitrogen is diatomic to some and polyatomic to others. Others are solids, whereas nitrogen is a gas.
The periodic table's third-period elements are known as typical elements because they do not exhibit anomalous properties with their respective groups. These are also known as representative elements. Sodium, magnesium, aluminium, silicon, phosphorus, sulphur, chlorine, and argon are among them.
Bridge elements are said to be entities from Period 2 of the periodic table. They are so named because they have diagonally identical properties, i.e. the elements of period 2 are similar to the elements of period 3's next category, namely lithium magnesium; beryllium; aluminium; boron silicon, and so on.
