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Group 15 p-block Elements – Nitrogen Family

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  • Last Updated : 24 Feb, 2022
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The final electron of a P block element enters one of the three p-orbitals of the shell in which it is found. There are six groups of p-block elements since a p-subshell has three degenerate p-orbitals, each of which may hold two electrons.

Because of their tendency to lose an electron, P block elements are lustrous and typically strong conductors of electricity and heat. In a P-block element like gallium, you may find some astonishing characteristics of elements. It’s a metal that melts in your palm. Because silicon is a key component of glass, it is also one of the most significant metalloids in the p-block group.

Group 15 Elements

From groups 13 through 18, the p-block elements are located on the right-hand side of the periodic table. The nitrogen family is made up of five elements: nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi). The general electronic configuration for group 15 is ns2np3.

Nitrogen

7

N

Phosphorus

15

P

Arsenic

33

As

Antimony

51

Sb

Bismuth

83

Bi

Occurrence of Group 15 Elements

  1. Nitrogen: 78 parts per million of air. It is the most significant member of this group and occurs as a diatomic gas, N2, in its free state.
  2. Both animal and plant stuff require phosphorus to function properly. Nucleic acids, such as DNA and RNA, contain phosphate groups. Phosphates make up around 60 percent of the makeup of bones and teeth.
  3. Phosphoproteins can be found in egg yolk, milk, and bone marrow. Arsenic, antimony, and bismuth, the other elements in the group, are mainly found as sulphides. Some examples are stibnite, arsenopyrite, and bismuth glance.

Trends in Group 15 Elements

  • Group 15 Elements Atomic Radii- The outermost shell of group 15 atoms has five electrons, the s-subshell has two electrons, and the p-subshell has three electrons. As you move down the group, the ionic and atomic radii grow as another primary energy level in each sequential element expands.

Element

Atomic 

Number

Electronic 

Configuration

Group

Number

Period 

Number

Nitrogen

7

2s2 2p3

15

2

Phosphorus

15

3s2 3p3

15

3

Arsenic

33

3d10 4s2 4p3

15

4

Antimony

51

4d10 5s2 5p3

15

5

Bismuth

83

4f14 5d10 6s2 6p3

15

6

  • Group 15 Elements Ionisation Enthalpy- The group 15 elements initial ionisation enthalpies are greater than those of the group 14 elements comparable members. They are more stable due to their larger atomic charge, lower nuclear radii, and stable half-filled electronic setups. As we progress through the group, the ionisation enthalpy values fall. This is related to the gradual expansion of atomic size.
  • Group 15 Elements Electronegativity- Electronegativity refers to a particle’s ability to draw a shared pair of electrons closer to itself. As one proceeds down the group, the electronegativity falls gradually due to the rise in atomic radius.
  • Group 15 Elements Metallic Character- The elements of Group 15 are less metallic. The metallic aspect becomes more evident as one proceeds down the group, from N to Bi. Non-metallic elements such as N and P are non-metallic, partially non-metallic elements such as As and Sb are partially non-metallic, and metals such as Bi are metals.
  • Group 15 Elements Melting and Boiling points- The melting point of this group rises from nitrogen to arsenic, then falls to antimony and bismuth. However, the boiling points grow continuously as one progresses from nitrogen to bismuth.

  • Group 15 Elements Density Points- From N to Bi, the density of these elements similarly rises.

  • Group 15 Elements Allotropy- All of the group fifteen elements, with the exception of bismuth, exhibit allotropy.
  1. There are two allotropic types of nitrogen: alpha nitrogen and beta nitrogen.
  2. Phosphorus occurs in a wide range of allotropic configurations. Red and white phosphorus are the two most significant allotropic structures.
  3. The allotropic structures of arsenic are black, grey, and yellow.
  4. Yellow, metallic, and explosive are three significant allotropic structures for antimony.
  • Group 15 Elements Oxidation States- This group of elements has five electrons in its outermost shell with oxidation states ranging from 3 to +5. The fundamental negative oxidation state of these elements is 3. As one proceeds down the group, the likelihood of exhibiting a 3 oxidation state reduces. Because of the increase in atomic size and metallic property, this is the case. By creating covalent bonds, Group 15 elements can also have positive oxidation states of +3 and +5. The stability of the +5 oxidation state reduces as one progresses down the group due to the inert pair effect, whereas the stability of the +3 oxidation state rises. The valance shell of nitrogen is made up entirely of s- and p-orbitals, with no d-orbitals. Nitrogen, as a result, has a maximum covalency of 4. It can acquire a covalency of four by sharing its lone pair of electrons with another atom or ion. The covalency of phosphorus with the remaining elements can range from five to six, also known as extended covalency. This is feasible due to the presence of unoccupied d orbitals in the valence shell. The compounds of group fifteen elements with a +5 oxidation state are all covalent. In the +3 oxidation state, ionic and covalent molecules are generated.

Anomalous Behaviour of Nitrogen

The attributes of the group’s major element differ from those of the other components in general. The characteristics of nitrogen are distinct from those of the other elements in the group. The following factors contribute to nitrogen’s extraordinary properties:

  1. Because of its modest nuclear size.
  2. High electronegativity or ionisation enthalpy.
  3. The absence of d-orbitals.
  4. The ability to develop a variety of relationships.

Property

Nitrogen

Phosphorus

Arsenic

Antimony

Bismuth

Atomic Symbol

N

P

As

Sb

Bi

Atomic Number

7

15

33

51

83

Atomic mass (amu)

14.01

30.97

74.92

121.76

209.98

Valence electron 

configuration

2s2 2p3

3s2 3p3

3d10 4s2 4p3

4d10 5s2 5p3

4f14 5d10 6s2 6p3

Melting point

Boiling point (oC)

-210

-196

44.15

281

817

603

631

1587

271

1564

Density (g/cm3) at 25o C

1.15

1.8

5.7

6.68

9.79

Atomic Radius (pm)

56

98

114

133

143

First Ionization Energy (KJ/mol) 

1402

1012

947

834

703

Common Oxidation state

-3 to +5

+5,+3,+3

+5,+3

+5,+3

+3

Ionic radius (pm)

146

212

58

76

103

Electronegativity

3.0

2.2

2.2

2.1

1.9

Uses of Group 15 Elements

  1. Nitrogen and phosphorus are two of the elements that are essential for life to exist.
  2. Nitrogen gas, N2, makes up the bulk of the Earth’s atmosphere. Like this, pnictides are diatomic pnictogen molecules. Because of their valency, pnictide atoms form a covalent triple bond.
  3. Phosphorus is found in a wide range of items, such as matches, pyrotechnics, and fertilizer. It is also used to manufacture phosphoric acid.
  4. Arsenic is a toxic substance. It has been employed as a poison as well as a rodenticide.
  5. Alloys are made with antimony.
  6. Bismuth is a chemical that may be found in medicines, paints, and as a catalyst.

Sample Questions

Question 1: What are the physical properties of group 15 elements?

Answer

  1. Polyatomic elements make up the whole group.
  2. The initial element, nitrogen, is a gas, but as the group progresses, the metallic aspect of the elements becomes increasingly apparent.
  3. Because of a drop in ionisation enthalpy and an increase in atomic size, bismuth is classified as a metal. Nonmetals include nitrogen and phosphorus, metalloids include arsenic and antimony, and bismuth is classified as a metal.
  4. Boiling points are often trending downward.
  5. Except for bismuth, all elements have allotropes.

Question 2: What are the atomic radii of group 15 elements?

Answer

The outermost shell of group 15 atoms has five electrons, the s-subshell has two electrons, and the p-subshell has three electrons. As you move down the group, the ionic and atomic radii grow as another primary energy level in each sequential element expands.

Question 3: Why are group 15 elements called pnictogens?

Answer

Pigeon means to choke or suffocate in Greek, hence Group 15 elements are called pnictogens. In the absence of oxygen, molecular nitrogen possesses this characteristic. As a result, group 15 elements are sometimes known as pnictogens or the nitrogen family.

Question 4: What are the allotropes of group 15? 

Answer 

The allotropes of group 15 are :

  1. There are two allotropic types of nitrogen: alpha nitrogen and beta nitrogen.
  2. Phosphorus occurs in a wide range of allotropic configurations. Red and white phosphorus are the two most significant allotropic structures.
  3. The allotropic structures of arsenic are black, grey, and yellow.
  4. Yellow, metallic, and explosive are three significant allotropic structures for antimony.
  5. Bismuth does not have any allotropes.

Question 5: What are the uses of group 15 elements?

Answer

  • Two elements that are required for life to exist are nitrogen and phosphorus.
  • The majority of the Earth’s atmosphere is made up of nitrogen gas, or N2. Pnictides are diatomic pnictogen molecules in the same way. Pnictide atoms form a covalent triple bond due to their valency.
  • Phosphorus may be found in a variety of products, including matches, pyrotechnics, and fertilizer. It’s also utilised in the production of phosphoric acid.
  • Arsenic is a poisonous metal. It’s been used as both a poison and a rodenticide.
  • Antimony is used to make alloys.
  • Bismuth is a chemical that is used in pharmaceuticals, paints, and as a catalyst.

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