The elements are classified into four blocks in the long form of the periodic table: \({\rm{s,p,d}}\), and \({\rm{f}}\), depending on the subshell into which the last electron enters.

Representative elements or main group elements are the elements in the s and p blocks of the periodic table. They are divided into two sections, with groups \(1\) to \(2\) and \(13\) to \(18,\) respectively. The s-block elements are in groups \(1\) and \(2,\) while p-block elements are in groups \(13\) to \(18.\)

This article will study everything about the atomic and physical properties of a group in the p-block, that is, group \(15\)- Nitrogen family.

Group 15 Elements

The p-block elements are placed on the right-hand side of the periodic table from groups \(13\) to \(18.\)

Group \(15\) is called the nitrogen family, and it includes five elements which are nitrogen \(\left( {\rm{N}} \right)\) phosphorus \(\left( {\rm{P}} \right)\), arsenic \(\left( {{\rm{As}}} \right)\), antimony \(\left( {{\rm{Sb}}} \right)\) and bismuth \(\left( {{\rm{Bi}}} \right)\)

The general electronic configuration for group \(15\) is \({\rm{n}}{{\rm{s}}^{\rm{2}}}{\rm{n}}{{\rm{p}}^{\rm{3}}}.\)

Occurrence of Group 15 Elements

Nitrogen: \(78%\) by volume of air. It is the most important member of this group and exists in a state as a diatomic gas, \({{\rm{N}}_{\rm{2}}}.\)

Phosphorus is an essential component of both animal and plant matter. Phosphate groups are found in nucleic acids such as DNA and RNA. Phosphates account for approximately \(60\%\) of the composition of bones and teeth.

Egg yolk, milk, and bone marrow all contain phosphoproteins. The remaining elements in the group, namely arsenic, antimony, and bismuth, are mostly found as sulphides. Stibnite, arsenopyrite, and bismuth glance are a few examples.

Trends in Group 15 Elements

The trends in Group 15 elements are explained below:

Group \(15\) Elements Atomic Radii

The atoms of group \(15\) have five electrons in the outermost shell, two electrons in the s-subshell and three electrons in the p-subshell.

The ionic and atomic radii increase on moving down the group due to expanding another main energy level in each progressive element.

Group 15 Elements Ionisation Enthalpy

The first ionisation enthalpies of the group \(15\) elements are higher than the corresponding members of the group \(14\) elements. Because of their higher atomic charge, smaller nuclear radii, and stable half-filled electronic setups, they are more stable. The ionisation enthalpy values decrease as we move down the group. This is due to the progressive increase in atomic size.

Group 15 Elements Electronegativity

The tendency of a particle to attract a shared pair of electrons more towards itself is referred to as electronegativity. Because of the increase in atomic radius, the electronegativity decreases bit by bit as one moves down the group. 

Group 15 Elements Metallic Character

Group \(15\) elements are less metallic. However, as one moves down the group, the metallic character becomes more prominent, from \({\rm{N}}\) to \({\rm{Bi}}\)

\({\rm{N}}\) and \({\rm{P}}\) for example, are non-metallic, As and Sb are partially non-metallic, and \({\rm{Bi}}\) is a metal.

Group 15 Elements Melting and Boiling points

This group’s melting point increases from nitrogen to arsenic, then decreases to antimony and bismuth. However, as one moves from nitrogen to bismuth, the boiling points rise steadily.

Group 15 Elements Density Points

The density of these elements also increases from \({\rm{N}}\) to \({\rm{Bi}}.\)

Group 15 Elements Allotropy

Except for bismuth, all of the group fifteen elements show allotropy.

1. Nitrogen exists in two allotropic forms: alpha nitrogen and beta nitrogen.
2. Phosphorus can be found in a variety of allotropic structures. The two most important allotropic structures are red phosphorus and white phosphorus.
3. Arsenic has three basic allotropic structures: black, grey, and yellow.
4. Antimony also has three important allotropic structures, namely yellow, metallic, and explosive.

Group 15 Elements Oxidation States

The elements of this group have \(5\) electrons in their outermost shell, and they exhibit various oxidation states from \(-3\) to \(+5.\)

These elements have a basic negative oxidation state of \(-3.\) The tendency to exhibit \(-3\) oxidation state decreases as one moves down the group. This is due to the increase in atomic size and metallic character.

Group \(15\) elements also show positive oxidation states of \(+3\) and \(+5\) by forming covalent bonds. Because of the inert pair effect, the stability of the \(+5\) oxidation state decreases as one moves down the group, while the stability of the \(+3\) oxidation state increases.

Nitrogen’s valance shell contains only \({\rm{s}}\)- and \({\rm{p}}\)-orbitals and no \({\rm{d}}\)-orbitals. As a result, nitrogen has a maximum covalency of \(4.\) By sharing its lone pair of electrons with another atom or ion, it can achieve a covalency of four.

Phosphorus and the remaining elements can have a covalency of five and a maximum covalency of six, also known as expanded covalency. Because of the presence of vacant \({\rm{d}}\) orbitals in the valence shell, this is possible. All group fifteen elements’ compounds with a \(+5\) oxidation state are covalent.

Ionic and covalent compounds are formed in the \(+3\) oxidation state.

Anomalous Behaviour of Nitrogen

In general, the properties of the principal element of any group differ from those of the other elements. Nitrogen’s properties differ from other elements of the group. Nitrogen’s exceptional properties are attributed due to the following:

1. Its small nuclear size,
2. High ionisation enthalpy or electronegativity, 
3. Lack of d-orbitals,
4. Ability to form various types of bonds.

These periodic table trends help us better understand the behaviour of atoms. Below given is the table for trends of the group \(15\) elements:

Uses of Group 15 Elements

Some of the uses of group \(15\) elements are as follows:

1. Two of the elements, nitrogen and phosphorus, are required for life to exist.
2. The majority of the Earth’s atmosphere is made up of nitrogen gas, \({{\rm{N}}_{\rm{2}}}\). Pnictides are diatomic pnictogen molecules like this. A covalent triple bond links pnictide atoms due to their valency.
3. Phosphorus is used in a variety of products, including matches, fireworks, and fertiliser. It is also used in the production of phosphoric acid.
4. Arsenic is poisonous. It’s been used as both a poison and a rodenticide.
5. Antimony is used to make alloys.
6. Bismuth is a chemical that is used in medications, paint, and as a catalyst.

Summary

In this article, we studied that physical state, metallic character, melting and boiling points, density, and allotropy are all examples of physical properties. Except for nitrogen, which is a diatomic gas, the remaining elements are solids. The metallic nature of the elements rises as we travel down a group, but the ionisation enthalpy of the elements reduces as their atomic size increases. Except for bismuth, we currently know that elements in this group have an oxidation state ranging from \(-3\) to \(+5.\) They also have allotropes.

FAQs on Atomic and Physical Properties of Group 15 Elements

Q.1. What are the physical properties of group 15 elements?
Ans: Some of the physical properties of group \(15\) are as follows:
i. All of the elements in the group are polyatomic.
ii. The first element, nitrogen, is a gas, but on moving down the group, the metallic character of the elements increases significantly.
iii. Nonmetals are nitrogen and phosphorus, metalloids are arsenic and antimony, and bismuth is metal due to a decrease in ionisation enthalpy and an increase in atomic size.
iv. In general, boiling points show an increasing trend of moving down.
v. All elements, except for bismuth, have allotropes.

Q.2. What are the atomic radii of group 15 elements?
Ans: The atoms of group \(15\) have five electrons in the outermost shell, two electrons in the s-subshell and three electrons in the p-subshell. The ionic and atomic radii increase on moving down the group due to expanding another main energy level in each progressive element.

Q.3. Why are group 15 elements called pnictogens?
Ans: Group \(15\) elements are known as pnictogens because pigeon means to choke or suffocate in Greek. Molecular nitrogen has this property in the absence of oxygen. As a result, group \(15\) elements are referred to as either the nitrogen family or pnictogens.

Q.4. How many elements are there in group 15?
Ans: Group \(15\) is called the nitrogen family, and it includes five elements which are nitrogen \(\left( {\rm{N}} \right)\) phosphorus \(\left( {\rm{P}} \right)\), arsenic \(\left( {{\rm{As}}} \right)\), antimony \(\left( {{\rm{Sb}}} \right)\) and bismuth \(\left( {{\rm{Bi}}} \right)\)

Q.5. Discuss the allotropes of group 15 elements briefly.
Ans: The allotropes of group \(15\) are as follows:
i. Nitrogen exists in two allotropic forms: alpha nitrogen and beta nitrogen.
ii. Phosphorus can be found in a variety of allotropic structures. The two most important allotropic structures are red phosphorus and white phosphorus.
iii. Arsenic has three basic allotropic structures: black, grey, and yellow.
iv. Antimony also has three important allotropic structures, namely yellow, metallic, and explosive.
v. Bismuth has no allotropes.

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