Group 15 Elements Definition

Nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth are all members of the nitrogen family of chemicals (Bi). The electron configuration ns2np3 is found in the outer shells of all Group 15 elements, where n is the primary quantum number. Group 15’s p-block contains the nitrogen family.

Chemical Properties

All Group 15 elements tend to follow the general traits:

• As the group progresses, electronegativity (the capacity of an atom to attract electrons) declines.
• The amount of energy required to remove an electron from an atom in its gas phase decreases as you progress down the group.
• The size of atomic radii grows as the group progresses.
• Down the group, electron affinity (an atom’s capacity to take an electron) declines.
• Melting point (the amount of energy required to break bonds to convert a solid phase substance to a liquid phase substance) rises as you progress through the group.
• The boiling point (the amount of energy required to break bonds and convert a liquid to a gas) rises as the group progresses.
• The group becomes more metallic as it progresses.

Physical Properties

(1) Atomic and ionic radii: Group 15 elements have smaller atomic and ionic radii than group 14 elements. As the atomic number decreases, the atomic radii decrease.

Group 15 elements have a higher nuclear charge than group 14 elements. The electrons are strongly drawn by the nucleus as the nuclear charge increases, and atomic radii shrink as a result. As a result, group 15 elements have smaller atomic radii than group 14. Moving down the group, the atomic radii rise due to the inclusion of a new primary shell in each succeeding element, resulting in an increase in the number of shells. However, the covalent radius increases just little from As to Bi. This is because the heavier members have entirely filled d and/or f-orbitals.

(2) Ionization enthalpies: The initial ionisation enthalpies of group 15 elements are greater than those of group 14 elements.

Ionisation enthalpies fall as you progress down the group.

The greater nuclear charge, small size, and stable arrangement of the atoms of group 15 elements account for the higher ionisation enthalpy.

Atoms in group 15 have half-filled electronic configurations, npx1, npy2, and npz1, which are stable. As a result, their ionisation enthalpies are quite high.

As we advance down the group, the drop in ionisation enthalpy is owing to an increase in atomic size and the screening effect, which outweighs the effect of increasing nuclear charge.

(3) Electronegativity: Group 15 elements have higher electronegativity values than group 14 elements.

The electronegativity value falls as you move along the group.

Explanation: Group 15 elements have smaller atoms with a higher nuclear charge, hence their electronegativity values are higher.

The decrease in electronegativity as the group number increases is due to the larger atoms and the shielding effect of the inner electron shells.

(4) Metallic character: Group 15 elements have a lower metallic character. The metallic character, on the other hand, increases from N to Bi as you move down the group.

For example, non-metallic elements N and P, partly non-metallic elements As and Sb, and metal elements Bi are all non-metallic elements.

Group 15 elements are less metallic than group 14 elements due to increased nuclear charge and higher electronegativity.

The atomic size, as well as the screening effect of the intervening electrons, grows as one moves down the group. As a result, the ionisation enthalpy reduces as the group progresses, and the metallic character rises.

(5) Melting and boiling points: From nitrogen to arsenic, the melting points of group 15 elements increase, then decrease until antimony and bismuth are reached. When travelling from nitrogen to bismuth, however, the boiling points climb steadily.

Explanation: Due to the increase in atomic size, melting points rise as you progress through the group. The surprising drop in melting points of Sb and Bi is due to the inert pair effect, which causes them to form three rather than five covalent bonds. As a result, their atoms have a weak affinity to one another, resulting in low melting points. Bi has less interatomic interactions than Sb because of its larger atom size, and so has a lower melting point. Because of the increase in atomic size, the boiling temperatures rise as the group progresses from N to Bi.

(6) Catenation: Group 15 elements have a proclivity for forming connections with themselves (self-linking of atoms), which is known as catenation. Two N atoms are bound together in hydrazine (H2NNH2), three N atoms are bonded together in hydrazoic acid (N3H), and three N atoms are bonded together in azide (N3-). Azide ion and hydroxyazoic acid

Phosphorus has the highest potential for catenation among the elements in group 15, creating cyclic and open chain compounds with numerous phosphorus atoms.

Because of their lower (M-M) bond dissociation enthalpies, elements in group 15 have a lower potential to show catenation than carbon.

(7) Allotropy: All other elements in this group have allotropy except nitrogen and bismuth.

As an illustration:

1. a) There are three types of phosphorus: white, black, and red.
2. b) There are two types of arsenic: yellow and grey.
3. c) Antimony can be found in allotropic forms that are yellow or silvery grey.

Group 15 elements are also called Nitrogen family

All nitrogen compounds are ultimately produced from the unusually stable N2(g) nitrogen gas. The electronic structure of N2(g) is stable because the bond between the two nitrogen atoms is a triple covalent bond that is strong and difficult to break. Breaking the bonds in N2 causes a large endothermic enthalpy change: H = +945.4 kJ. Nitrogen gas is utilised as a refrigerant, as well as a metal treatment and as a pressured gas for oil recovery. Furthermore, the Gibbs energies of nitrogen compound production reveal that the process is nonspontaneous and does not happen at room temperature.

Nitrous oxide (N2O), nitrogen oxide (NO), and nitrogen dioxide are the oxides and oxyacids of nitrogen (NO2). Nitrous oxide, popularly known as “laughing gas,” is used in dental procedures, childbirth, and to speed up automobiles. Smog and neurotransmitters both include nitrous oxide. N2H4 (hydrazine) is a toxic, colourless liquid that explodes when exposed to air. Hydrazine is an excellent reducer, and methyl hydrazine is a frequent rocket fuel.

Conclusion 

Scheele and Priestley first discovered nitrogen in 1770. This non-metallic element is found in nature as a non-combustible gas with no colour, taste, or odour. Nitrogen has the highest electronegativity of all the elements in Group 15, making it the most non-metallic. Nitrogen has the following oxidation states: +5, +3, and -3. Nitrogen makes up around 0.002% of the earth’s crust, yet it makes up 78% of the atmosphere by volume. In the atmospheres of Venus and Mars, nitrogen has also been identified. The atmospheres of Venus and Mars contain 3.5 percent nitrogen and 2.7 percent nitrogen, respectively. Animal and plant proteins, as well as the fossilised remains of ancient plant life, contain nitrogen. Niger, KNO3, and soda nitre, NaNO3, are major nitrogen-containing minerals that can be found in desert areas and are used in fertilisers. Nitrogen supplies were scarce before the discovery of the process of turning nitrogen into ammonia. The Haber-Bosch process is a crucial step in the conversion of nitrogen to ammonia. The solubility of nitrogen in liquids is quite low. Allotropes do not exist in N2.