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Group 15 Elements:

Group 15 elements are also called the Nitrogen family. It includes nitrogen, phosphorus, arsenic, antimony and bismuth elements. The p-block elements are also known as the Representative Elements which are placed on the right side of the main periodic table.

Elements of Nitrogen family are known as Pnictogens (refer to choking).

General electronic configuration of Pnictogens: ns²np³.

The ionization enthalpy of the nitrogen family is much greater than that of carbon family due to extra stability of half-filled configuration.

Periodic Trends in Group 15 Elements:

So in Group 15 elements as you would move down a group, starting with the lightest element and finishing with the heavy ones; you’d notice a general flow in properties as you move down the order. For example: Nitrogen is a gas and non-metal but as you move down the group, we encounter metalloids and then at the bottom, metal i.e. Bismuth. These trends in the periodic table help us better understand the behavior of atoms and also helps us predict new elements.
 

Some of the trends in the modern periodic table with respect to group 15 elements of the p-Block elements are discussed below:

1. Electronic Configuration:
 

• The valence shell electronic configuration plays a major role in how an element behaves. The valence electron shell configuration of group 15 elements is ns²np³.
• All the group 15 elements have the same arrangement and this is why they’re similar.
• The s-orbital in this group is completely filled and the p-orbitals are half filled and this makes their configuration extra stable.
  
   

2. Atomic and Ionic Radii:
 

• If you see the electronic configuration of elements in the table above, you will notice that with every step you move downwards, new orbitals are added to the atom.
• This addition of new orbitals increases both the Atomic and the Ionic radii of group 15 elements.
• However, we see that from Arsenic to Bismuth only a small increase in ionic radius is observed.
• This is due to the presence of completely filled d and/or f orbitals in heavier members.
  
   

3. Ionization Enthalpy:
 

• Ionization Energy is the amount of energy required to remove an electron from the outermost orbit of the atom.
• This is basically a measure of how hard the nucleus is holding on to the electron.
• The closer the electron is to the nucleus the stronger its hold and thus the energy required is more.
• As we move down the group, the radius of the atom increases, and therefore the Ionization energy decreases due to the weaker hold of the nucleus.
  
   

4. Electronegativity:
 

• The electronegativity value decreases down the group with increasing atomic size.
• This again is due to the increasing distance between the nucleus and the valence shell as we move down the group.
  
   

5. Physical Properties:
 

• All the elements of the group exist in a polyatomic state.
• First, Nitrogen is gas, but as you move down, there is a significant increase in the metallic character of the elements.
• Nitrogen and Phosphorus are non-metals, Arsenic and Antimony are metalloids and Bismuth is a metal.
• These changes can be attributed to the decrease in Ionization enthalpy and increase in atomic size.
• Boiling points also, in general, show an increasing trend as you move down.
• Except for Nitrogen, all the other elements have allotropes.
  
   

6. Chemical Properties:
 

• The valence shells of the p-Block elements have a configuration of ns² np³.
• So the elements here can either lose 5 electrons or gain 3.
• The common oxidation states of these elements are -3, +3 and +5.
• With a decrease in the Ionization enthalpy and electronegativity due to the increasing atomic radius, the tendency to gain three electrons to create a -3 oxidation state decreases down the group.
• In fact, Bismuth hardly forms any compounds with a -3 oxidation state.
• As we go down, the stability of the +5 state decreases and that of +3 increases due to the inert pair effect.
  
   

7. Electron Affinity:
 

• Electron affinity is zero for nitrogen.
• Other elements have negative value of electron affinity due to availability of vacant d orbital.
   

Apatite Family:

Apatite families can be described as a group of similar isomorphous hexagonal phosphate minerals. The main apatite group consists of Fluorapatite, Chlorapatite, and Hydroxylapatite. The teeth and bones of various animals, including humans, are composed of Calcium phosphate, which is also the same material as apatite.

The primary Apatite group includes Fluorapatite, Chlorapatite, and Hydroxylapatite. The extended Apatite supergroup describes additional minerals such as Pyromorphite, Mimetite, and Vanadinite. Apatite is the main source of phosphorous, an important nutrient required by plants. As such, apatite is the key ingredient in phosphate fertilizers. Most of the phosphorus used in fertilizer comes from phosphate rock, which is mined almost exclusively for this application.

Practice these questions in order to test your knowledge about Group 15 elements:

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Group-16 Elements:

The group 16 elements of the modern periodic table consist of 5 elements oxygen, sulphur, selenium, tellurium and polonium. The elements in this group are also known as the chalcogens or the ore-forming elements because many elements can be extracted from sulphide or oxide ores.

Oxygen is abundantly found on the earth. Estimating the proportions of different types of atoms found in the universe, oxygen was claimed as the fourth abundant element after hydrogen, helium, and neon. It constitutes about 89% of water, 46% of the earth crust and 20 % of the air. The group 16 elements are as follows:

Oxygen:

The chemical symbol for oxygen is given as O. It is a colorless and odorless gas used in the respiration process by humans, which is converted into carbon dioxide. Oxygen exists as a diatomic molecule (O₂). Oxygen is also found as a triatomic molecule (O₃) in traces, it is known as ozone. Oxygen combines readily with many elements. During the combination with some elements, the evolution of heat energy takes place, this process is known as combustion.

 

Sulphur:

Sulphur is denoted by the symbol S. It is a non-metal which ranks ninth on the basis of cosmic abundance. About 1 atom in every 20,000-30,000 atoms is a sulphur atom. Sulphur is found in the combined state as well as in the free state. About 0.09 % of sulphur is found in seawater in the form of sulphates. The meteorite contains 12 % of sulphur, a large amount of sulphur is found from the underground deposits of pure sulphur present in dome-like structures. Here sulphur is formed by the action of anaerobic bacteria on the sulphate minerals such as gypsum.

 

Selenium:

Selenium is rarer than oxygen or sulphur. It is found in the free state as well as in the combined state with heavy metals (such as lead, silver, or mercury) in a few minerals. The Grey metallic form of selenium is the most stable form of the element under normal conditions.

 

Tellurium:

Tellurium is a chemical element having atomic number 52 and has the properties between metals and non-metals. It is one of the rarest stable elements found in the earth’s crust. It is often found in a free state and in compounds with elements such as copper, lead, silver or gold.

 

Polonium:

It is the rarest element among elements of group 16. It is a radioactive element. Polonium is sometimes used in scientific applications for alpha radiation.